Where does “reit” come from?

reit (Old French) comes from Old French roide, from Old French roit, from Latin rigidus, from Latin -idus, from Proto-Italic *-iðos.

Ancestry of “reit”, step by step

Step	Language	Word	Meaning
1	Old French	roide	—
2	Old French	roit	hard
3	Latin	rigidus	stiff, rigid, hard, inflexible; stern, strict,...
4	Latin	-idus	tending to
5	Proto-Italic	*-iðos	—

reit — Etymology, Origin & Word History | Etymology Explorer