- informal a long time
WordReference Random House Unabridged Dictionary of American English © 2026
don′key's years′, [Informal.]
- Informal Termsa very long time;
eons.
- probably origin, originally donkey('s) ears, as rhyming slang for years, with years replacing ears once rhyming origin, originally was forgotten 1895–1900
Collins Concise English Dictionary © HarperCollins Publishers::
donkey's years n