IPA: /ˈbækˌhaʊs/
KK: /ˈbækˌhaʊs/
A structure located at the back of a main building, often used for storage or other purposes.
The gardener keeps all the tools in the backhouse behind the main house.
Backhouse → The word is formed from "back" (from Old English "bæc", meaning the rear or behind) and "house" (from Old English "hus", meaning a dwelling or shelter). A backhouse refers to a structure located at the rear of a property, often used for storage or as a secondary dwelling.
Think of a 'house' ('hus') that is located at the 'back' ('bæc') of a property — that's what a backhouse is.