Where does “treuage” come from?

treuage (Old French) comes from Old French -age, from Old Occitan -atge, from Latin -āticum.

Ancestry of “treuage”, step by step

Step	Language	Word	Meaning
1	Old French	-age	forms nouns with the sense of 'action or result...
2	Old Occitan	-atge	suffix used to form masculine nouns
3	Latin	-āticum	—