overflown

From over- +‎ flown.

overflown

1. past participle of overfly

From Middle English overflowen (past participle of overflowen besides rare overflowed), from Old English oferflōwen (past participle of oferflōwan).

overflown

1. (sometimes proscribed) past participle of overflow

• The use of overflown as the past participle of overflow is sometimes proscribed due to being perceived as a conflation between overfly and overflow. However, it was once more prevalent throughout the English-speaking world, and is ultimately the original form.