c.1200, "legal and administrative body of ancient Rome," from O.Fr. senat
or L. senatus
"highest council of the state in ancient Rome," lit. "council of elders," from senex
) "old man, old" (see senile
). Attested from late 14c. in reference to governing bodies of free cities in Europe; of national governing bodies from 1550s; specific sense of upper house of U.S. legislature is recorded from 1775.