Word Origin & History
"emotional condition, frame of mind," O.E. mod "heart, frame of mind, spirit, courage," from P.Gmc. *motha- (cf. O.Fris. mod "intellect, mind, courage," O.N. moðr "wrath, anger," M.Du. moet, Du. moed, O.H.G. muot, Ger. Mut "courage," Goth. moþs "courage, anger"), of unknown origin. A much more
vigorous word in Anglo-Saxon than currently, and used widely in compounds (e.g. modcræftig "intelligent," modful "proud"). To be in the mood "willing (to do something)" is from 1580s. First record of mood swings is from 1942.
"grammatical form indicating the function of a verb," 1569, an alteration of mode
(1), but the grammatical and musical (1597) usages of it influenced the meaning of mood (1) in phrases such as light-hearted mood.