the word 'topaz' entered english via old french 'topace' and latin 'topazus', which was borrowed from ancient greek 'topazos'. the greek term likely originated from the name of an island in the red sea, topazios (now zabargad or st. john's island), which was a historical source for a yellow-green stone, though not necessarily the modern mineral we call topaz. the meaning has shifted and stabilized over centuries to refer specifically to the aluminum silicate fluoride hydroxide mineral known for its hardness and variety of colors. its journey from a geographical place-name to a general term for a gemstone exemplifies a common pattern in the history of mineral names.

the word is a simplex loanword. it does not contain separable morphemes within its modern english spelling.