Loom means a utensil. (Anglo-Saxon, loma). Thus “heir-loom” means a personal chattel or household
implement which goes by special custom to the heir. The word was in familiar use in Prior's time
(1664-1721), for he says “a thousand maidens ply the purple loom.”

I never thought of "heir-loom" before. But what on earth is a "purple loom"?