An exceptionally hard crystalline form of carbon.
A familiar word, four lives.
Greek
adamas
‘name of a hypothetical hardest material’
into Latin
Latin
adamas
‘hardest metal, diamond’
into Late Latin
Late Latin
diamas
into Middle French
Middle French
diamand
into Middle English
Middle English
diamaunde
became English
English
diamond
The diamond name runs through Latin adamas, its later alteration diamas, and French diamand. Middle English diamaunde is an additional stage before the modern spelling. The sequence concerns the word’s forms, not the date people first encountered the mineral.
These are selected stages, not every spelling or intermediary. The story identifies omitted links; older forms did not all disappear at once.
The oldest form is less immediately recognisable than the later spelling changes.