Why is the ninth month called September?
late 15c., "to settle," from Middle French resider (15c.) and directly from Latin residere "sit down, settle; remain behind, rest, linger; be left," from re- "back, again" (see re-) + sedere "to sit" (see sedentary). Meaning "to dwell permanently" first attested 1570s. Related: Resided; residing. Also from the French word are Dutch resideren, German residiren.