Unpaid comes from un- ('not') + paid, the past participle of pay, from Old French paier, from Latin pacare ('to appease, pacify'), from pax ('peace'). The historical chain includes Old English un-, Latin pacare, and Latin pax. The quoted older senses, "not", "to appease, pacify", and "peace", supply the semantic anchors for unpaid. The formation is best read as compound, participial, and borrowed: the word unpaid carries its older form-history into a compact English lexical shape. In present English it is used as a adj, "not yet paid; working without payment". Related English forms include pay, paid, payment, and unpay. The result is a adj whose etymology preserves both the older form and the later English specialization.