word-forming element in scientific compounds meaning "cartilage," from Latinized form of Greek khondros "cartilage" (of the breastbone), also "grain, grain of salt, seed, barley-grain," of uncertain origin. This is sometimes said to be from the PIE root meaning "to grind" which is the source of English grind (v.), but there are serious phonological objections and the word might be non-Indo-European [Beekes, "Etymological Dictionary of Greek"]. The body material so called for its gristly nature.
"stack of hay," Old English muga, muwa "a heap (of grain, pease, etc.), swath of corn; crowd of people," earlier muha, from Proto-Germanic *mugon (source also of Old Norse mugr "a heap," mostr "crowd"), of uncertain origin. Meaning "place in a barn where hay or sheaves of grain are stored" is by 1755.
Middle English repere (early 14c. in surnames), "a harvester, one who cuts grain with a sickle or other instrument," replacing Old English ripere, agent noun from reap (v.). Sense of "a machine for cutting grain" is by 1841. As the name of a personification of death, by 1818.