Where does “mercat” come from?

mercat (Old Occitan) comes from Latin mercatus, from Latin -tus, from Proto-Italic -tus, from Proto-Indo-European -tus — Derives action nouns from verb roots.

Ancestry of “mercat”, step by step

Step	Language	Word	Meaning
1	Latin	mercatus	trade, traffic, buying and selling; market,...
2	Latin	-tus	Forms the past participle of verbs; Forms...
3	Proto-Italic	-tus	—
4	Proto-Indo-European	-tus	Derives action nouns from verb roots

Every word from Proto-Indo-European -tus →Every word from Latin -tus →Every word from Latin mercatus →