The Collaborative International Dictionary of English v.0.48:
Stainer \Stain"er\ (-[~e]r), n. 1. One who stains or tarnishes. [1913 Webster] 2. A workman who stains; as, a stainer of wood. [1913 Webster]WordNet (r) 3.0 (2006):
stainer n 1: a worker who stains (wood or fabric)