tyrant

Tyrant comes from Middle English tyraunt or tiraunt, borrowed from Old French tyrant. That French form added a final -t to an earlier tiran, likely under the influence of Latin present participles ending in -ans, and traces back to Latin tyrannus ("despot"), from Ancient Greek τύραννος (túrannos, "usurper, monarch, despot"), a word of unknown origin.

The Old French spelling shifted from tiran to tyrant by borrowing a -t ending pattern associated with Latin participles, even though tyrannus itself wasn't a participle — a change in shape rather than meaning as the word passed into Middle English.

It shares its Latin root, tyrannus, with the modern French word tyran, showing how the two languages diverged slightly in spelling from the same Greek ancestor.