pet form of masc. proper names Edward, Edmund, and Theodore; meaning "women's undergarment" (with lower-case t-) is recorded from 1924, of unknown origin, perhaps from some fancied resemblance to a
teddy bear (q.v.), a theory that dates to 1929. In British slang phrase teddy boy (1954) it is short for Edward, from the preference of such youths for Edwardian styles (1901-10). Teddies (probably from Teddy Roosevelt) was one of the names given to U.S. troops in France in 1917.