There are quite a few questions on the main site related to (first-order) Peano Arithmetic and its fragments. Here are two examples: 1, 2 (but there are many others).
It would be nice, and feels appropriate, to have a tag devoted to them. Currently, they are tagged "logic", usually with an additional tag ("number theory", "arithmetic", "model theory", ...)
A dedicated tag would help locate these questions more easily, cross-reference them, etc. As a result, I believe it would certainly make them more useful in the long run.
I would appreciate suggestions for how to name this new tag (or reasons why such a tag is a bad idea or unnecessary). If we decide to go ahead with a new tag, there is then the question of whether some of the current tags should be removed from the questions, or if we simply add the new one to them.
If a consensus is reached, I can carry out the (re)tagging (just three or so questions a day for a few days, to avoid cluttering the front page).