Billhook is a compound of bill ('a cutting tool, a hooked blade', from Old English bil) + hook (Old English hōc), referring to the curved blade. The historical trail runs through bil in Old English and hōc in Old English. Morphologically, billhook is transparent: it is a compound of bill ('a cutting tool, a hooked blade', from Old English bil) + hook (Old English hōc), referring to the curved blade. Used as a noun, billhook now means "a curved blade on a handle, used for pruning and cutting brush", so the present definition can be read against the older forms and meanings. The same lexical family is also visible in related forms such as bill and hook. The modern word remains analyzable through its parts, which makes the semantic connection unusually direct.