Where does “soubrire” come from?

soubrire (Middle French) comes from Old French sorrirre, from Vulgar Latin subridere, from Latin subrīdēre.

Ancestry of “soubrire”, step by step

Step	Language	Word	Meaning
1	Old French	sorrirre	—
2	Vulgar Latin	subridere	present active infinitive of subrīdeō;...
3	Latin	subrīdēre	—