onychan.

Etymology: < post-classical Latin onycha ingredient of incense consisting of the opercula of marine molluscs (Vulgate) < Hellenistic Greek ὄνυχα , accusative of ὄνυξ onyx n. (see also note below). The Greek word in the accusative occurs in the Septuagint in Exodus 30:34; in the nominative ὄνυξ in Ecclus. 24:16; in the latter case the Vulgate renders it ungula, but in the former leaves onycha in its Greek form; this, being apparently not recognized as the accusative of onyx, was treated by medieval writers as a distinct word (in post-classical Latin onica (13th cent.), onicha, treated as indeclinable or as feminine of first declension); hence in English versions of the Bible. Compare Anglo-Norman onicha, Old French onica (late 12th cent.), Old French, Middle French onique (13th cent.).This sense of Greek ὄνυξ, apparently due to the resemblance of the πῶμα κογχυλίου ‘lid of a shell’, or operculum, to a finger-nail, occurs in Dioscorides 1. 2, where also mention is made of its fragrant odour ‘resembling castor to some degree’ when burnt.