The word pantywaist is an American appellation for an effeminate young man is not much more than thirty years old.
The idea, however, takes us back to about 1890.
Small American children, then, and some perhaps not so small, were encased in a sleeveless undervest, bedecked with buttons at the waistline, to which their panties were severally attached.
The garments were for children and, especially, for girls; ergo, feminine and non-heroic.
