Modern dagger fashioned after the kind which became popular in the 17th century, shaped like a medieval sword.
A dagger is essentially double-edged knife, where the tang is placed along the center line of the blade. The word 'dagger' may have come from Vulgar Latin word 'daca' - a Dacian knife.
Although not technically a dagger, the rondel, a stabbing weapon with triangular or rectangular cross-section, is commonly included in the term.
Some daggers also have weighted blades, and are meant for throwing at enemies. The weighted blade provided momentum and accuracy.
A dagger is more a weapon made for thrusting than a tool for slicing and cutting.
The earliest daggers appear in the Bronze Age, in the 3rd millennium BC, predating the sword, which essentially developed from oversized daggers. Daggers were important secondary weapons in Europe during the Middle Ages and the renaissance.
A modern version of the dagger is the bayonet, which becomes a spear type weapon when mounted on the barrel of a rifle.
The principal medievaldagger was the misericorde, which from the end of the 12th century was used, in all countries in which chivalry flourished, to penetrate the joints of the armour of an unhorsed adversary (hence Ger.
The distinction between the dagger and the poniard is arbitrary, and in ordinary language the latter is taken as being the shorter and as having less resemblance to a short sword or cutlass.
The Scottish "dirk" was a long dagger, and survives in name in the dirk worn by midshipmen of the royal navy, and in fact in that worn by officers of Highland regiments.
Although the standard dagger would at no time be very effective against axes, spears or even maces due to its limited reach, it was an important step towards the development of a more useful close combatweapon: the sword.
The increasing sophistication of sword fighting and a prevailing sense of chivalrous honour caused knives and daggers to lose their popularity as weapons in medieval times, only to regain it during the Renaissance in the form of the Stiletto, which proved to be very effective against the plated body armor popular at the time.
Daggers achieved public notoriety in the 20th Century as ornamental uniform regalia during the fascist dictatorships of Mussolini's Italy and Hitler's Germany, but dress daggers were used by several other countries as well, including Japan.