late 14c. (late 13c. as a surname), collere "charcoal maker and seller," agent noun from Middle English col (see coal). They were notorious for cheating their customers. Meaning "digger in a coal mine" is from 1590s. Sense of "coasting-vessel for hauling coal" is from 1620s.
-y 1
noun suffix, in army, city, country, etc., from Old French -e, Latin -atus, -atum, past participle suffix of certain verbs, which in French came to be used to indicate "employment, office, dignity" (as in duché, clergié).