Where does “Senate” come from?

Senate (English) comes from Middle English senat, from Old French senat, from Latin senātus, from Latin -ātus, from Proto-Italic -ātos, from Proto-Indo-European -éh₂tos — Forms adjectives from nouns, indicating the possession of a thing or a quality.

Senate (English): Any of several legislative bodies. In countries which have multiple legislative bodies, the Senate is often the more senior