French word trancher comes from Vulgar Latin *trinicare, and later Old French trenchier (To cut (make an incision).)

Detailed word origin of trancher

Dictionary entry	Language	Definition
*trinicare	Vulgar Latin (la-vul)
trenchier	Old French (fro)	To cut (make an incision).
trancher	French (fra)	(intransitive) to rule, make a ruling, come to a decision. (intransitive, pejorative, with de) to behave or comport oneself (as if one were). (intransitive, with avec, sur) to contrast (with), stand out (against). (intransitive, with dans) to stand out (in). (transitive) to slice, to cut into slices. (transitive, figurative) to decide, to settle, to address. (transitive, literary) to [...]