[1] The kerkouros is frequently glossed (Harpocration, Hesychius, Photius, the Lexica Segueriana, the Etymologicum Magnum, Glosses on Herodotus 7.97, Herodian De prosodia catholica vol. 3.1 p. 202), all with some variation of "kind of boat" or "kind of ship".
[2] Tzetzes, Chiliades 6.47, writing a couple of centuries later, gives a listing of twelve types of boat; ke/rkouroi come first, le/mboi kai\ muopa/rwnes fifth and sixth. Appian, Libyca 576 mentions ke/rkouroi and muopa/rwnes together as small boats.
[3] The proverb is actually ko/rxoros e)n laxa/nois "a blue pimpernel among herbs", on which see kappa 2133. (Adler does not comment on this mis-reading of a scholion on Aristophanes, Wasps 239.)