"swollen state, expansion," 1650s, from French intumescence (17c.), from Latin intumescere "to swell up, rise, be elevated," of sounds, "grow louder," figuratively, "grow excited, become enraged," from in- "in" (from PIE root *en "in") + tumescere "begin to swell, swell up," figuratively "grow excited, become enraged," inceptive of tumere "to swell" (from PIE root *teue- "to swell"), with inchoative suffix -escere.
