Etymology: Middle English welle, from Old English; akin to Old English weallan to bubble, boil, Old High German wella wave, Lithuanian vilnis
Date: before 12th century
1 a: an issue of water from the earth : a pool fed by a spring b:source, origin 2 a: a pit or hole sunk into the earth to reach a supply of water b: a shaft or hole sunk to obtain oil, brine, or gas 3 a: an enclosure in the middle of a ship's hold to protect from damage and facilitate the inspection of the pumps b: a compartment in the hold of a fishing boat in which fish are kept alive 4: an open space extending vertically through floors of a structure 5: a space having a construction or shape suggesting a well for water 6 a: something resembling a well in being damp, cool, deep, or dark b: a deep vertical hole c: a source from which something may be drawn as needed 7: a pronounced minimum of a variable in physics <a potential well>