An Etymological Dictionary of Astronomy and Astrophysics

A suffix denoting “action, process, state, or condition,” and corresponding to adjectives ending in -escent. → luminescence.

Etymology (EN): From L. -escentia, from escens, from esse “to be,” → existence, + -ia

Etymology (PE): -esti, noun from -est, variant of ast, hast “is, → exists,” cognate with L. -escence, as above.