Greek word
sardónyx
σαρδόνυξ
What it means
hence the onyx stone)
hence the "onyx" stone); a "sardonyx", i.e. the gem so called
Where it comes from
from the base of sárdios (σάρδιος) and (the nail of a finger
How the King James translates it
Every place it appears 1
Revelation21:20