Origin and history of fled

Old English fleon, flion "take flight, fly from, avoid, escape" (contracted class II strong verb; past tense fleah, past participle flogen), from Proto-Germanic *fleuhanan "to run away" (source also of Old High German fliohan, Old Norse flöja, Old Frisian flia, Dutch vlieden, German fliehen, Gothic þliuhan "to flee"), probably from PIE *pleuk-, extended form of root *pleu- "to flow," but Boutkan is not convinced. Also compare fly (v.2).

Weak past tense and past participle fled emerged in Middle English under influence of Scandinavian. Old English had a transitive form, geflieman "put to flight, banish, drive away," which came in handy in the Anglo-Saxon Chronicle. Related: fled; Fleeing.

"run away," Old English fleon, flion "fly from, avoid, escape;" in this use the modern word is essentially a variant spelling of flee (q.v.).

In Old English, this verb and fleogan "soar through the air with wings" (modern fly (v.1), q.v.) differed only in their present tense forms and often were confused.

They have been distinguished from one another since 14c. in the past tense: flew (occasionally flied) for fly (v.1), fled for fly (v.2).

To fly the coop "escape, depart at once" is U.S. colloquial attested by 1887, a reference to caged birds and etymologically perhaps involving both verbs.