Mania comes from Greek 'manía' (madness), from the PIE root *men- (to think), linking the concepts of thinking and insanity.
Mental illness marked by periods of great excitement or euphoria, delusions, and overactivity; an excessive enthusiasm or desire, an obsession.
From Latin 'mania' (madness, frenzy), borrowed directly from Greek 'manía' (madness, frenzy, enthusiasm), from the verb 'maínesthai' (to rage, to be mad), from PIE *men- (to think, to use one's mind) — with the ironic twist that the same root that gives us 'mind,' 'mental,' and 'memory' also underlies words for madness, since intense mental states and their loss share the same ancestral word-field. The PIE root *men- is one of the most productive in Indo-European: Sanskrit 'manas' (mind, spirit), Latin 'mens' (mind), Old English 'gemynd' (mind, memory), and Gothic 'muns' (thought) all derive from it. Greek 'mania' entered English in the 15th century