Refers to a person used by someone else to do their bidding, often in a manipulative or subordinate way. Commonly appears in the phrase お先棒を担ぐ (to act as someone's cat's-paw).
From お先棒を担ぐ, literally “to carry the front pole”: 先棒 was the front pole of a palanquin and, by extension, its front bearer. The expression developed the figurative sense of serving as another person’s agent or tool.
