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1833; see monomania + maniac. Related: Monomaniacal.
"insanity in regard to a single subect or class of subjects," 1820, probably on model of earlier French monomanie, from Modern Latin monomania, from Greek monos "single, alone" (see mono-) + mania (see mania).
monomania mon·o·ma·ni·a (mŏn'ə-mā'nē-ə, -mān'yə)n. Pathological obsession with one idea or subject, as in paranoia.