http://www.baseball-reference.com/teams/MIN/
You're wrong. The team was NEVER officially called that, local "pet nicknames" aside, the Washington Senators were the Senators. Baseball Reference is the definitive resource on team names and statistical histories on the internet.
The Senators won the 1925 world series and there are plenty of news articles from then that refer to them by that name.
Where did you pull this misinfo from????? By the way back in those days (the oughts and teens of the 1900's), NO team really had ANY name. When radio announcers spoke of a National league team they said "nats" and for american league teams, "americans". Or they referred to the team by its local nickname. The Dodgers, for example, were known as the Robins and so on. The Senators.... never had another pet name and I can find no solid example of anyone ever having called them the "nats", not to say nobody did, I wasn't fucking alive then. They were in the American League. I have a TON of original baseball materials from that era and NONE say anything but Senators.
/baseball historian