reduplicate (v.)

"to double again, multiply, repeat," 1560s, from Medieval Latin reduplicatus, past participle of reduplicare "to redouble," from re- "back, again" (see re-) + Latin duplicare "to double" (see duplicate (adj.)). In linguistics, "to repeat, as a syllable or the initial part of a syllable (usually a root syllable)." Related: Reduplicated; reduplicating; reduplicative.