ETYM Old Eng. welle, AS. wella, wylla, from weallan to well up, surge, boil; akin to Dutch wel a spring or fountain. Related to Well.
1. A deep hole or shaft dug or drilled to obtain water or oil or gas or brine.
2. An abundant source; SYN. wellspring, fountainhead.
3. An open shaft through the floors of a building (as for a stairway).
4. An enclosed compartment in a ship or plane for holding something as e.g. fish or a plane's landing gear or for protecting something as e.g. a ship's pumps.