Three naming conventions real teams use: Northern Comets, Portland Vipers, or Savage Falcons. Pick the one that suits the competition.
Sports naming is more conventional than it looks and the three styles here cover most of it. The club form puts a qualifier in front of a mascot (Northern Comets, Real Ironworks) which is the European football pattern and reads as an established institution. The city form pairs a place with a plural mascot, the North American convention, and instantly signals a franchise. The adjective form drops the geography entirely and just describes the team, which is what pub quiz sides and five-a-side teams actually do because they have no place to represent.
A team name gets shouted, abbreviated and printed on things, and those uses punish different weaknesses. Long names get truncated on a league table. Names whose initials spell something unfortunate get discovered by the opposition within a week. Names that depend on a joke about a current situation age badly by the third fixture. The safest picks are two or three syllables total, with initials you have actually looked at, and no reference to anything that will be out of date by the end of the season.
The adjective form. Club and city styles imply a place you represent, which a workplace or friends team does not have.
Two or three syllables. Longer names get truncated on league tables and scoreboards, and abbreviated by everyone regardless.
Some combinations will exist somewhere. Search before you register with a league, particularly if there is any chance of a trademark clash.