IPA: //ˈkʌstəmhaʊs//
KK: /ˈkʌstəmˌhaʊs/
A government building where taxes on goods brought into or taken out of a country are collected, and where ships are allowed to enter or leave.
The cargo was inspected at the customhouse before it could be delivered.
Customhouse → The word is formed from "custom" (from Old French *costume*, meaning a habit or practice) and "house" (from Old English *hus*, meaning a dwelling or shelter). A customhouse is a building where customs duties are collected and where goods are inspected for compliance with regulations.
Think of a 'house' where 'customs' are managed — that's why a customhouse is a place for handling customs duties.