The story
- Latin · derived fromanecdotum
- English todayanecdotum
Back-formation from anecdota, reinterpreting the nominative neuter plural case ending -a as a Latin case ending (singular: -um), rather than (as is etymologically-consistent) as an Ancient Greek case ending (singular: -on, from -ον (-on)); perhaps reinforced by Latin anecdotum.
Etymology from Wiktionary, CC BY-SA 4.0.