The headword, a neuter noun, is attested only in lexicography. Its earliest appearance, in Hesychius epsilon4908, is uninformative, as the headword is simply glossed with an even rarer noun (e)pikoru/fwma, a crowning or culminating element); however, the Suda entry is very similar to later ones, in Etymologicum Gudianum 505.9 and Etymologicum Magnum 361.8. The headword appears in quite a different sense in Eustathius' commentary on Homer, Odyssey 8.311, where it stands as a synonym for kataku/llwma. Eustathius says that both these forms are attested as Attic by Aristophanes of Byzantium (fr. 71 Nauck) in the apparent sense of "deformation" (or the like). These terms are adduced as an explanation for kullopodi/wn (usually taken as 'club-footed'), Hephaestus's epithet at Homer, Iliad 21.331. It is possible that the various forms and meanings associated with the word here and in Eustathius represent contamination between words derived from the near synonyms kullo/s and kolobo/s, which share no recognizable etymological connection.
[1] cf. kappa 1940.
[2] In Et.Gud and Et.Magn. (see first note above) one finds in this place not just kollou/rion but i)atriko\n kollou/rion ('physician's breadroll'), apparently in reference to a probe, suppository, pessary or salve. See LSJ s.v. kollu/rion (web address 1).