Compared to Fermat's two squares theorem, or Fermat's four squares theorem, Fermat's Little theorem is indeed Little.
Not to mention the hard-to-prove Fermat Last Theorem, which goes under FLT(so that acronym, or a contraction Flt) isn't suitable.
Therefore one might as well stick with "Fermat's Little Theorem" itself. I have given above a reasoning that it is comparatively little.