IPA: /ˈwɛlˌhoʊl/
KK: /ˈwɛlˌhoʊl/
A space or cavity in a structure, often used for a staircase or to hold a counterbalancing weight in machinery.
The wellhole in the building allowed for a beautiful staircase to be installed.
Wellhole → The word is formed from "well" (from Old English *wella*, meaning a spring or source of water) and "hole" (from Old English *hol*, meaning a hollow place). A wellhole refers to a hollow place that serves as a source of water, typically a deep hole dug to access groundwater.
Think of a 'spring' or 'source' of water ('well') that is found in a 'hollow place' ('hole') — that's what a wellhole is.