Boyd’s Bible Dictionary:
(nail). Incense ingredient; probably burnt seashell (Ex. 30:34).
Concise Bible Dictionary:
One of the ingredients of the holy “perfume” which was burnt as incense (Ex. 30:34). The Hebrew is shecheleth; onycha is from the Greek ὄνυξ, “nail or claw,” and it is supposed to refer to the operculum or claw of one or more species of the Strombus, a shell fish: the claw gave a sweet odor when burnt.
Strong’s Dictionary of Hebrew Words:
Transliteration:
shcheleth
Meaning:
apparently from the same as 7826 through some obscure idea, perhaps that of peeling off by concussion of sound; a scale or shell, i.e. the aromatic mussel.
Jackson’s Dictionary of Scripture Proper Names:
whose travail: roaring (as a lion)