"state of prolonged unconsciousness," 1640s, from Latinized form of Greek kōma (genitive kōmatos) "deep sleep," which is of uncertain origin. A term for "coma" in Middle English was false sleep (late 14c.). Related: Comal.
"nebulous, hair-like envelope surrounding the head of a comet," 1765, from Latin coma, from Greek komē "hair of the head," which is of unknown origin. Earlier in English as a botanical term for a tuft of hairs (1660s). For the constellation Coma Berenices, see Berenice. Related: Comal.