FROM STRONG’S GREEK DICTIONARY (1890)

Strong’s Greek Dictionary (1890) — public domain, printed whole.

sardonux σαρδόνυξ — sar-don'-oox — from the base of 4556 and onux (the nail of a finger; hence the "onyx" stone); a "sardonyx", i.e. the gem so called:-- sardonyx.

see GREEK for 4556