early 13c., as a noun, "complaint, lamentation," probably related to O.E. mænan "complain, moan," also "tell, intend," from P.Gmc. *main- (but OED discounts this connection). Meaning "long, low inarticulate murmur from some prolonged pain" is first recorded 1670s. The verb is first attested early 15c. as "to complain," 1724 as "to make a low, mournful sound." Related: Moaned; moaning.