Bullheaded is a compound of bull + headed, evoking the brute stubbornness of a bull. Bull is from Middle English bole, of Germanic origin; head from Old English heafod. The historical trail runs through bole in Middle English and heafod in Old English. Morphologically, bullheaded is transparent: it is a compound of bull + headed, evoking the brute stubbornness of a bull. Used as an adjective, bullheaded now means "obstinately and unreasonably stubborn", so the present definition can be read against the older forms and meanings. The same lexical family is also visible in derived forms such as bullheadedness and bullheadedly and related forms such as bull and headed. The modern word remains analyzable through its parts, which makes the semantic connection unusually direct.