galley slave
noun
1- historical a person condemned to man the oars in a galley〈史〉（战舰上）划桨的奴隶（或囚犯）。
1.1
- a person who works very hard, typically performing menial or thankless tasks（尤指吃力不讨好的）苦力, 做苦工的人：
call-centre workers are the galley slaves of the twenty-first century.
呼叫中心的工作人员是21世纪吃力不讨好的苦力。