sidneySidney (often shortened to Sid) is an English given name deriving from the surname, itself of two different derivations depending on the orins of the family. In some cases a place name, itselfSidney is a city in and the county seat of Richland County, Montana, United States, [4] less than 10 mi (16 km) west of the North Dakota border. The population was 6,346 at the 2020 census.