culm

Etymology 1

Perhaps related to coal. 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: compare Old English culme.

noun

1. waste coal, used as a poor quality fuel; slack.
   Here he lay down on a place soft with culm, to take his contemplated rest, and, before he was aware of it, sleep had descended on him, overpowered him, and bound him fast. 1887, Homer Greene, chapter XXI, in Burnham Breaker
2. anthracite, especially when found in small masses

Etymology 2

Borrowed from Latin culmus. Doublet of calame, calamus, and haulm; further related to caramel, chalumeau and shawm.

noun

1. (botany) the stem of a plant, especially of grass or sedge
   […] because, upon hearing him out, she sank down on the lawn in an impossible posture, examining a grass culm and frowning, he had taken his words back at once; […] 1962, Vladimir Nabokov, Pale Fire, page 150