late 14c., "flame-like in appearance;" c.1400, "on fire," present participle adjective from flame, v.. Meaning "of bright or gaudy colors" is from mid-15c. As an intensifying adjective, late 19c. Meaning "glaringly homosexual" is homosexual slang, 1970s (along with flamer (n.) "conspicuously homosexual man"); but flamer "glaringly conspicuous person or thing" (1809) and flaming "glaringly conspicuous" (1781) are much earlier in a general sense, both originally with reference to "wenches." Related: Flamingly.