Crossbow (lat. Arbalista, Arcubalista), a medieval missile weapon evolved from the bow (the Greek hand-held crossbow gastraphetes is thought to have been developed prior to 420 B.C.). It consists of a wooden tiller or stock (primarily ash or yew) with a steel or baleen bow (called prod or lath), the ends of which are connected by a string made of sinew, hemp, or linen whipcord. Inside the shaft is a rolling cylindrical nut with a perpendicular slot for the projectile, an axial slot which holds the string, and a lower slot where the trigger or tickler sits. Pushing the trigger lever up releases the nut which rolls forward and releases the string. The string is pulled forward by the prod, hits the projectile lying in the groove of the stock (bolt, quarrel, or bullet) and shoots it. Light crossbows could be drawn by hand, heavier ones were hooked to the soldiers's belt and drawn by placing one foot in a stirrup at the front of the stock and straightening the leg. Hinged levers, cranequins, or windlasses were used to cock the heavier crossbows. The invention of the lever and ratchet drawing mechanisms allowed mounted troops to shoot, draw and reload crossbows on horseback.
In the defence of cities and castles, large crossbows (arcuballistas) of 7-9 m length were placed on the platforms of gates and towers, and they were mounted on carriages to serve as field artillery.
The balester light crossbow (German Schnäpper, s. illustration) with short steel prod had a device which caught the string or cocking lever when the crossbow was drawn. Some crossbows had a covered groove or a cylindrical iron barrel, with a notch guiding the string, designed to shoot bullets made of kiln fired clay, marble or lead capable of penetrating armour at ranges up to 250 paces. This explains why the crossbow remained the preferred shooting weapon for a long time, even after firearms had been introduced. The arquebus was probably named after a crossbow firing rocket-like bolts. The crossbow was known in France as early as the 9th century, and it became popular in Germany in the 12th century, achieving such success that it's use against Christians was prohibited by the Second Council of the Lateran in 1139. The crossbow disappeared from the armies' inventories in the mid-16th century, but it's still being used at target shooting competitions even today.
Source: Meyers Großes Konversations-Lexikon, 6. Auflage 1905–1909