Meaning

noun stem of plants of the Gramineae

originFrom Middle English culme, colme (“fragments of coal”), of uncertain origin. Probably from Old English *colm, related to Old English col (“coal”). Alternatively, perhaps from Welsh cwlm (“knot or tie”), applied to this species of coal, which is much found in balls or knots in some parts of Wales.

Etymology from Wiktionary, CC BY-SA 3.0