Bald
Middle English: probably from a base meaning ‘white patch’, whence the archaic sense ‘marked or streaked with white’. Compare with Welsh ceffyl bal, denoting a horse with a white mark on its face.
wiktionary
From Middle English balled, ballid, bald(“bald”), of uncertain origin. Probably formed from Middle English bal, balle(“ball, round object, knoll, head”). Compare with Old Danish bældet(“bald”).
Alternate etymology has Gothic 𐌱𐌰𐌻𐌰-( bala-, “shining, grey (of body)”), Old English bǣl(“fire, flame; funeral pyre”) (both from Proto-Germanic *bēlą), Albanian balë(“white spot on the forehead”) and ball(“forehead”).
etymonline
bald (adj.)
c. 1300, ballede, "wanting hair in some part where it naturally grows," of uncertain origin. Perhaps with Middle English -ede adjectival suffix, from Celtic bal "white patch, blaze" especially on the head of a horse or other animal (from PIE root *bhel- (1) "to shine, flash, gleam"). But Middle English Compendium says probably formed on the root of ball (n.1) and compares Old Danish bældet.
Compare, from the same root, Sanskrit bhalam "brightness, forehead," Greek phalos "white," Latin fulcia "coot" (so called for the white patch on its head), Albanian bale "forehead." But connection with ball (n.1), on notion of "smooth, round" also has been suggested, and if not formed from it it was early associated with it. Sometimes figurative: "meager" (14c.), "without ornament" (16c.), "open, undisguised" (19c.). Of automobile tires with worn treads, by 1930. Bald eagle first attested 1680s; so called for its white head.
