"close growth of hair on the chin and lower face, normally characteristic of an adult male" (that of the upper lip being distinguished in Modern English as the mustache), Old English beard "beard," from Proto-Germanic *bard (source also of Old Frisian berd, Middle Dutch baert, Old High German bart, German bart), said in Pokorny to be from a PIE root *bhardhā- "beard" (source also of Old Church Slavonic brada, Russia boroda, Lithuanian barzda, Old Prussian bordus, and perhaps Latin barba "beard"), but Boutkan rejects this on phonetic grounds and suggests a non-IE substrate word. Old French berd is from Germanic.
The Greek and Roman Churches have long disputed about the beard. While the Romanists have at different times practised shaving, the Greeks, on the contrary, have strenuously defended the cause of long beards. Leo III. (795 AD) was the first shaved Pope. Pope Gregory IV., after the lapse of only 30 years, fulminated a Bull against bearded priests. In the 12th century the prescription of the beard was extended to the laity. Pope Honorius III. to disguise his disfigured lip, allowed his beard to grow. Henry I. of England was so much moved by a sermon directed against his beard that he resigned it to the barber. Frederick Barbarossa is said to have been equally tractable. [Tom Robinson, M.D., "Beards," St. James's Magazine, 1881]
Pubic hair sense is from 1600s (but neþir berd "pubic hair" is from late 14c.); in the 1811 "Dictionary of the Vulgar Tongue," the phrase beard-splitter is defined as, "A man much given to wenching" (compare beaver in the slang genital sense).