donkey work
noun
Informal. tedious, repetitious work; drudgery.
Also don·key·work [dong-kee-wurk, dawng‐, duhng‐] /ˈdɒŋ kiˌwɜrk, ˈdɔŋ‐, ˈdʌŋ‐/.
Origin of donkey work
First recorded in 1915–20
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019