There is a word: ( Lewis & Short at the Perseus Project )
B. Subst.: annŭum , i, and more freq. in the plur.: annŭa , ōrum, n., an annuity, annual stipend, pension: “publici servi annua accipiunt,”
... and can it be mere coincidence that a pension is involved ? "super" would be in the sense of "beyond" ... an extended pension.
A+++
Excellent analysis, but way above my pay grade (which, incidentally, is zero.)