IPA: /ˈbækˌbreɪkər/
KK: /ˈbækˌbreɪkər/
A very difficult or exhausting task that requires a lot of effort.
Completing the marathon was a real backbreaker for the runners.
Backbreaker → It is formed from "back" (from Old English "bæce", meaning the rear part of the body) and "breaker" (from Old English "brecan", meaning to break). The word "backbreaker" refers to something that is so heavy or difficult that it can cause a person's back to break under the strain.
Think of the 'back' as the rear part of the body that can be 'broken' under heavy strain — that's why a backbreaker is something that can cause such a burden.