Middle English accidie, accyde, borrowed from Anglo-French, borrowed from Medieval Latin accidia, alteration of Late Latin acēdia — more at acedia
Note:
The forms with [i] in the medial syllable, apparently attested in the early Middle Ages (in the 8th-century Second Corpus Glossary of Old English), appear to show influence of Byzantine or earlier pronunciation of Greek (in which eta and iota merge), but it also has been suggested that the word has been assimilated to Latin accidere (see accident); however, the semantic grounds for such assimilation are unclear.
