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.
"of two different colors, having spots or patches of white and black or another color," 1580s, formed from pie (n.2) "magpie" + bald in its older sense of "spotted, white;" in reference to the black-and-white plumage of the magpie. Hence, "of mixed character, heterogeneous, mongrel" (1580s). Properly only of black-and-white colorings (compare skewbald).
1650s, "having white and brown (or some other color) patches, spotted in an irregular manner" (used especially of horses), from skued "skewbald" (mid-15c.), of unknown origin, + bald "having white patches" (see bald). First element said to be unconnected with skew (v.) (but Klein's sources say it is); OED suggests perhaps from Old French escu "shield," but also notes a close resemblance in form and sense with Icelandic skjottr, "the history of which is equally obscure." Watkins says it is Scandinavian and akin to Old Norse sky "cloud" on the resemblance of the markings to cloud cover.
When the white is mixed with black it is called 'pie-bald,' with bay the name of 'skew-bald' is given to it. ["Youatt's 'The Horse,' " 1866]
As a noun meaning "skewbald horse" from 1863.
