I've given up on receiving my unpaid wages.

Literal

Unpaid salary's receipt [object-を] gave-up.

未払い ('unpaid') uses the prefix 未- ('not yet') — a productive formal prefix attaching to nouns/verbs to indicate non-occurrence: 未完成 (unfinished), 未成年 (underage), 未知 (unknown). 諦める takes the abandoned thing with を.