It's definitely a matter of taste, but I feel like settling for "similar except different somehow" is the same thing as "couldn't think of a better name". I would much prefer f-strict because then I don't need to be familiar with the punctuation conventions of the codebase to know how it's different from f, it's right there in English.
Edit: Plus, then you don't have to wonder if that particular function follows that naming convention; prime meaning strict isn't nearly as universally followed as ? or ! in Scheme, for instance.