Origin and history of baldy

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").

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. Middle English Compendium says it probably was formed on the root of ball, and compares Old Danish bældet.

Sometimes figurative: "meager" (14c.), "without ornament" (16c.), "open, undisguised" (19c.). Of automobile tires with worn treads, by 1930. Bald eagle is attested by 1680s; so called for its white head.

diminutive suffix used in forming in pet proper names (Christy, Sandy, Jemmy), attested by c. 1400 in Scottish (as -ie). Perhaps it is a merging of the common adjective ending -y (2) with old fem. suffixes in -ie. It might have been reinforced by Dutch -je in similar use.

According to OED (1989) it became frequent in English 15c.-16c.

The use with common nouns, childish names of animals (Jenny wren), etc., also seems to have begun in Scottish (laddie is by 1540s) and become popular in English from late 18c. via Burns (timrous beastie). But the formation perhaps appears earlier in baby and puppy, and compare hobby in hobby-horse. Granny, dearie, and sweetie all are 17c. and early 18c.

In general use with names of girls (Kitty, Jenny), where it coincides with names such as Mary, Lucy, Lily, where it is not a diminutive. The extension to surnames seems to be from c. 1940.