The headword -- future active indicative, first person singular, of skimali/zw -- occurs at Aristophanes, Acharnians 444, and much of the entry derives from commentary to this passage. For another form of the same verb see epsilon 3150, where the same function is ascribed to a different finger. See also Phrynichus the Atticist fr. 353, Moeris sigma48 (both of whom explain the word as an Atticism); scholia to Aristophanes, Acharnians 444 and Peace 549, Hesychius sigma988, Photius sigma329 Theodoridis. Note that Henderson 213 #470 defines the verb as '[h]olding up the little finger', which 'meant, as it still does, that the recipient of the gesture was a pathic'. See also Henderson 213 #471.
[1] An adaptation of Diogenes Laertius 7.17, an anecdote from the life of Zeno of Citium. In the original the two other men are reclining below Zeno (u(panakeime/noin), which makes better sense of the action that follows. Here we find present active participle, genitive singular masculine, of the headword verb. LSJ suggest in this instance that the word be translated 'kicking', but since this meaning is not attested elsewhere, it seems likely that the headword is being used as an obscene exaggeration for comic effect, even if no implication of actual anal penetration on either man's part is intended.