The words concúpiscent, concúpiscence, concúpiscible seem to be irregularly stressed (at least, according to their dictionary pronunciations; regularized pronunciations apparently have been heard "in the wild") when compared to words like reminíscent(-ce), dehíscent(-ce), oblivíscible, immíscible, permíscible, not to mention a lot of other words with -éscent(-ce).
I found this exception mentioned in the fourth edition of John Walker's "Critical Pronouncing Dictionary" (1846), but there is no explanation given. The Oxford English Dictionary entries for these three words also don't explain the pronunciation.
Has anyone attempted to do so?
I tried to think of possible reasons, and the only thing I could come up with is possible stress shift from an original Middle English concupiscént/concupiscénce (taken from the stress in French or in Latin concupiscentia) via the somewhat common pattern of putting secondary stress on alternating syllables. Whereas, presumably, the other -scent/-scence words either came into English at a later period, when word-final stress was no longer common, or their pronunciation was remodeled for some reason while that of concupiscence etc. was not.
The OED's earliest citation is "c1340," spelled "concupyscens" which does seem earlier than the first OED citation for "adolescence" ("?a1425") or "pubescence" (?a1425). I also wasn't able to find any earlier attested use of an "-escence" word in the Middle English Dictionary quotations.
Even if nobody knows about these specific words, I would appreciate any more general information on the stress patterns of words ending in -ence or -ance in Middle English, and how they may have changed in the development to present-day English.