A 19th-century Spanish dagger.
A Handbook for Travellers in Spain (1855), by Richard Ford, has a commentary on the knife culture that prevailed in that country at the time. When we read an account of an exotic land written by an English traveler in the 19th century we have to take everything with a grain of salt, but it is interesting nonetheless. Ford assumes a level of erudition among his readers that is way beyond mine, but I have looked up as many references as I could and added them as bolded notes or endnotes.
Albacete, Abula, owing to its central position, from whence roads and rails branch to Aragon, Murcia, Valencia, and Madrid, is a place of great traffic, and is a town of locomotives, from the English rail, the French dilly, to the Spanish donkey. . . . Albacete is called the Sheffield of Spain [i.e., the knife-making capital], as Chatelherault is of France; but everything is by comparison, and the coarse cutlery turned out in each, at whose make and material an English artisan smiles, perfectly answers native ideas and wants. The object of a Spanish knife is to "chip bread and kill a man," and our readers are advised to have as little to do with them as may be.
The puñal or cuchillo, like the fan of the high-bred Andaluza, is part and parcel of all Spaniards of the lower class. Few are ever without this weapon of offence and defence, which is fashioned like a woman's tongue, being long, sharp, and pointed. The test of a bad knife is, that it won't cut a stick, but will cut a finger (Cuchillo malo, corta el dedo y no el palo). This knife, the precise daga of the Iberians, is the national weapon: hence Guerra á Cuchillo [War to the knife] is the modern war-cry, "Castile expects that every knife this day will do its duty;" and such in fact was the truly Spanish war defiance which was returned at Zaragoza to the French summons to capitulate.
This "long double-edged" tool is either stuck, as the old dagger used to be, in the sash, or is worn in the breeches' side-pocket, or like the Greek heroes wore their [Greek lettering], down the "right thigh" (Judges 3:16); and so the anelace in Chaucer bore "a Shefeld thwitel in his hose," just as the Manolas, or Amazons of Madrid, las de Cuchillo en Hija, have the reputation of concealing a small knife -- steel traps set here -- in the garter of their right leg (boni soit qui mal y pense); for it long has been a notion that making a start with the left leg foremost boded ill-luck.
This "prostitute knife" is a little over six inches long.
This female trinket is also called a puñalico and higuela; the latter word strictly speaking, means a "petticoat bustle;" all these weapons, a sort of Skein Dhu, are Scotch cousins to the Mattucashlash dirk, which the Highlanders carried in their armpits: a feminine puñalico now before us has the motto, Sirbo á una dama, "I serve a lady" -- Ich dien ["I serve."].
A Scottish sgian dubh, which is worn in the top of the stocking. This lovely one is available here.
Gentlemen's knives have also what Shakespeare calls their "cutler poetry;" this is also a Moorish custom, for, in what appeared to be a mere scrolly ornament on a modern Albacete cuchillo, these Arabic words have been read - "With the help of Allah! I hope to kill my enemy." As the mottoes of swords are various, so those on knives abound, couched in an humbler tone; e. g. Soy de mi Dueño y Señor, "I am the property of my lord and master." They say also -- Cuando esta víbora pica, No hay remedio en la botica,-- "When this viper stings, there's no remedy in any apothecary's shop." When the Sistema, or constitución of 1820, was put down, royalist knives were inscribed Peleo á gusto matando negros, and on the reverse, "I die for my King; killing blacks is my delight." The words Negros and Carboneros have long been applied in Spain to political blackguards.
A classic navaja.The term navaja means any blade, from a razor to a penknife, that shuts into a handle: the navajas of Guadix, which rival the puñales of Albacete, have frequently a muelle or catch by which the long pointed blade is fixed, and thus become a dagger or hand bayonet. The click which the cold steel makes when sharply caught in its catch, produces on Spanish ears the same pleasing sensation which the cocking a pistol does on ours. These spring and catch tools, always prohibited by law, have always been made, sold, and used openly. The gypsies, being great hole-in-corner men and cutpurses, since the times of the Rinconetes y Cortadillos of Cervantes, and the patrons also of slang, and flashmen, have furnished many cant names to the knife, e. g. glandi, chulo, churri (charri is pure Hindee for a knife). La Serdanie, Cachas, dos puñales á una vez; the Catalans call the instrument el gannivete, canif. It is termed in playful metaphor la tia, my aunt; corta pluma, a penknife; monda dientes, a tooth-pick; the best makers are generally well known. Thus Sancho Panza, when he hears that Montesinos had pierced a heart with a puñal, exclaims at once, "Then it was made by Ramon Hozes of Seville."
The handles are adorned in a barbaric semi-oriental style, often with much inlaid work, mother-of-pearl and coarse niello. There is a murderous, business-like intention in the shape, which runs to a point like a shark or a pirate felucca. A Spanish cutler, when praising his wares, will say, Es bueno para matar, "This is a capital article for killing." So the navajas del santo oleo kill a man dead before he can receive extreme unction.
However unskilled the regular surgeons and Sangrados may be in anatomy and the practice of the scalpel, the universal people know exactly how to use their knife, and where to plant its blow; nor is there any mistake, for the wound, although not so deep as a well, nor so wide as a church door, "will serve." It is not unseldom given after the treacherous fashion of their Oriental and Iberian ancestors, by a stab behind, of which the ancients were so fearful, "impacatos a tergo horrebis Iberos" (Virg. Geor. iii. 408), and it is planted "under the fifth rib," and "one blow" is enough (2 Sam. 20:10). The blade, like the cognate Arkansas or Bowie knife of the Yankees, will "rip up a man right away," or like a ripe melon, as Sancho says (Don Quix. ii. 32), or drill him until a surgeon can see through his body. As practice makes perfect, a true Baratero [knife fighter], is able to jerk his navaja into a door across the room, as surely and quickly as a good shot does a rifle-ball; a Spaniard, when armed with his cuchillo for attack, and with his capa for defence, is truly formidable and classical.
Many of the murders in Spain must be attributed to the readiness of the weapon, which is always at hand when the blood is on fire: thus, where an unarmed Englishman closes his fist, a Spaniard opens his knife. Man, again, in this hot climate, is very inflammable and combustible; a small spark explodes the dry powder, which ignites less readily in damp England. No wonder, therefore, that the blow of this rascally instrument, a true puñalada de picaro, becomes fatal in jealous broils, when the lower classes light their anger at the torch of the furies, and prefer using to speaking daggers: then the thrust goes home, vitamque in valuere ponit. In jealous broils, which are not unfrequent, the common punishment is gashing the peccant one's cheek, which is called "marking," or painting - Ya estas señalada, Ta estas pintado, picaro! In legal language, pintado por la justicia means branded a rogue; in baker's lingo, "pan pintado," signifies bread ornamented with crosses and gashes. "Mira que te pego, mira que te mato," are fondling or furious expressions of a Maja to a Majo. The Seville phrase was "Mira que te pinto un jabeque;" "take care that I don't draw you a xebeck" (the sharp Mediterranean felucca). "They jest at wounds who never felt a scar," but whenever this jabeque has really been inflicted, the patient, but whenever this jabeque has really been inflicted, the patient, not having the face to show him or herself, and ashamed of the stigma, is naturally anxious to recover a good character and skin, the one cosmetic to remove such superfluous marks, in Philip IV's time, was cat's grease:
El sebo unto de gato,
Que en cara defienda los señales.
 This is a play on the signal Admiral Nelson sent his fleet before the Battle of Trafalgar: “England expects that every man shall do his duty.”
 Judges 3:16:
Now Ehud had made a double-edged sword about a cubit [about 18 inches] long, which he strapped to his right thigh under his clothing. He presented the tribute to Eglon king of Moab, who was a very fat man. After Ehud had presented the tribute, he sent on their way those who had carried it. But on reaching the stone images near Gilgal he himself went back to Eglon and said, “Your Majesty, I have a secret message for you.”
The king said to his attendants, “Leave us!” And they all left.
Ehud then approached him while he was sitting alone in the upper room of his palace and said, “I have a message from God for you.” As the king rose from his seat, Ehud reached with his left hand, drew the sword from his right thigh and plunged it into the king’s belly. Even the handle sank in after the blade, and his bowels discharged. Ehud did not pull the sword out, and the fat closed in over it. Then Ehud went out to the porch; he shut the doors of the upper room behind him and locked them.
 Geoffrey Chaucer. "The Reeve’s Tale," Canterbury Tales:
Ther was no man, for peril, dorste hym touche.A Sheffeld thwitel baar he in his hose.Round was his face, and camus was his nose;
A thwitel, or thwittle, was a small knife; a "whittle."
 “Evil be to him who evil thinks.”
 "Blacks" refers to anti-royalists in this context.
 Virgil, Georgics, 3.408: Virgil advises travelers to keep guard dogs:
Nor let the care of dogs be last in your thoughts, but feed swift Spartan whelps and fierce Molossians alike on fattening whey. Never, with them on guard, need you fear for your stalls a midnight thief, or onslaught of wolves, or restless Spaniards [brigands] in your rear.
 2 Samuel 20:10: Sancho Pancho: "[T]hey would have given him a slash that would have slit him down from top to toe like a pomegranate or a ripe melon; they were likely fellows to put up with jokes of that sort!"
But Amasa took no heed to the sword that was in Joab's hand: so he smote him therewith in the fifth rib, and shed out his bowels to the ground, and struck him not again; and he died. So Joab and Abishai his brother pursued after Sheba the son of Bichri.