"Teddy" Roosevelt (1858-1919), a noted big-game hunter, whose conservationist fervor… See origin and meaning of teddy bear.
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) "young street rowdy" it is short for Edward, from the ...