Where does “ociosité” come from?

ociosité (Middle French) comes from Latin otiositas, from Latin ōtiōsus, from Latin -ōsus, from Old Latin -ōssus.

Ancestry of “ociosité”, step by step

Step	Language	Word	Meaning
1	Latin	otiositas	leisure, idleness
2	Latin	ōtiōsus	—
3	Latin	-ōsus	—
4	Old Latin	-ōssus	—