A solid with an ordered internal structure; especially clear quartz.
A familiar word, four lives.
Greek
krýstallos
into Latin
Latin
crystallum
‘clear ice, rock crystal’
into Old French
Old French
cristal
into Middle English
Middle English
cristal
‘transparent quartz, object made from it’
became English
English
crystal
Crystal comes through French and Latin from Greek krystallos. The early word connected ice with transparent quartz. The modern spelling restores a visibly classical y, showing why the oldest-looking spelling is not necessarily the oldest English form.
These are selected stages, not every spelling or intermediary. The story identifies omitted links; older forms did not all disappear at once.
Spelling can move toward an older source even while a word’s usage keeps changing.