Name of an alleged rock or mineral, as to which vague, contradictory, and fabulous notions long prevailed.
A distinction was made in late Latin between adamentem and its variant diamantem - the first meaning "loadstone" and the second meaning "diamond". Some folk etymology was involved: it was thought that adamentem was derived from adamō "to have an attraction for", so the word was associated with magnets and loadstones. diamantem was borrowed into English as diamond thru Old French diamant.
The suffixed o-grade form *domh₂-o- became English tame.