"made to measure or order, done or made for individual customers," by 1830, from custom (n.).
late 14c., "private, pertaining to the self or to a self-conscious individual; performed by the individual himself," from Old French personal (12c., Modern French personnel), from Late Latin personalis "pertaining to a person," from Latin persona (see person).
The meaning "applicable to, directed at, or aimed at some particular person" (usually in a hostile manner) is attested from 1610s. Designating an official or employee attached to one's person (as in personal secretary) by 1928.
The noun sense of "newspaper item about private matters" is attested from 1888. As "a classified ad addressed to an individual," it is recorded from 1861. Personal computer is from 1976.
"organism of several forms; an individual organism which differs from others of the same group or species," 1828, from Greek polymorphos "of many forms" (see polymorphous). Related: Polymorphic (1816).