From the scholia to Aristophanes, Lysistrata 158: "As Pherekrates says [fr.179 Kock], to flay flayed skin" (see web address 1). The general import of the proverb (Apostolius 10.29), on the lines of flogging a dead horse, seems clear enough (cf. epsilon 384), but a sexual meaning is required in the play; line 158 comes in response to a question asking what the women will do (sc. for sex) if their husbands leave. J. Henderson, The Maculate Muse (New Haven 1975) 133 #117 and 222 #492 envisages generalized masturbation rather than, specifically, the use of a dildo, but he later reverses this preference (Aristophanes, Lysistrata, edited with introduction and commentary by Jeffrey Henderson [Oxford 1987] 86).