They're originally a Mystara/Known World race, introduced in the D&D Creature Catalog (the green softcover book with a cover featuring a number of wary adventurers looking into a cave entrance). It was a book that felt very British, the same kind of tone used in Night's Dark Terror - probably because of the involvement of Bambra and Morris et al.
Lupins were originally wolf-headed humanoids that hated werewolves and hunted them with silver weapons. The Red Steel setting expanded things a lot and gave them their own nation alongside the rakasta and tortles etc. Quite a shift, but not necessarily a bad one. Much more swashbuckling wolf-man action.
Cheers,
Cam