古フランス語のpiece(小片)、低俗ラテン語の*pettia(おそらく古ケルト語の*pett(小)、語源的にはpetit(パッチ)と同じ)から。
PIECE. A wench. A damned good or bad piece; a girl who is more or less active and skilful in the amorous congress. Hence the (Cambridge) toast, may we never have a PIECE (peace) that will injure the constitution. ["Dictionary of Buckish Slang, University Wit and Pickpocket Eloquence," London, 1811]