*knhsei/w is the expected desiderative of kna/w, but this is the only instance of the verb attested. The Classical desiderative is knhsia/w, occurring in the matching participle knhsiw=nta in Plato, Gorgias 494C (which actually provides its own gloss: a)fqo/nws e)/xonta tou= kna=sqai). Timaeus' Platonic Lexicon and Photius kappa822 Theodoridis provide knhsiw=nta with the present gloss, so the Suda has simply regularised Plato's verb.