Why is the ninth month called September?
c.1300, ballede, probably, with Middle English -ede adjectival suffix + Celtic bal "white patch, blaze" especially on the head of a horse or other animal (from PIE root *bhel- (1) "to shine, flash, gleam;" see bleach (v.)). Cf., 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. Bald eagle first attested 1680s; so called for its white head.
adj. bald·er, bald·est
Lacking hair on the head.