If you peruse Baseball Reference long enough, you might stumble onto the Phillies’ franchise page.
The Phillies played their inaugural season in the National League in 1883, but according to the site they were known as the Quakers through '89. It is interesting then that the Phillies are sometimes called the “oldest, continuous, one-name, one-city franchise” in baseball.
So, what gives?
Well, a team called the Philadelphia Quakers joined the National Association in 1873. The league, however, folded in '75. The NL formed a year later, but the National Association’s Philadelphia A’s joined it. The A’s, however, got booted from the NL after refusing to take a road trip late in the season. The NL eventually wanted to re-establish itself in Philadelphia, so it disbanded the Worcester (Mass.) Brown Stockings (also known as the Ruby Legs) and formed a new franchise in Philadelphia in '83.
They were called the Phillies.
They were also called the Quakers, too. Unofficially, it seems.
Former Phillies vice president of communications Larry Shenk’s research staff (OK, the Baron is a one-man show) flipped through “The Philadelphia Phillies,” a book written by Fred Leib and Stan Baumgartner and published in 1953. (It was the only book in the Phillies’ PR office when Shenk joined the organization in '63.) In the book, Leib and Baumgartner wrote, “By general consent, the new team (1883) came to be known as the Phillies, one of the most natural and spontaneous of all big league nicknames. It was easily understood, as any oaf could recognize a Phillie to be a player from Philadelphia. However, the nickname of the old National Association Philadelphias -- the Quakers -- persisted, and for years a number of Philadelphia dailies referred to the new ball team as the Quakers.”
“Phillies: An Extraordinary Tradition” is the official history book of the franchise. In it, Bob Warrington confirmed that original owner Al Reach named the franchise the Phillies because “it tells you who we are and where we are from.”
The Phillies officially became the Phillies in 1890.