oppa (adverb) = a second time, twice
Daniel Garrison Brinton, Ancient Nahuatl Poetry: Containing the Nahuatl Text of XXVII Ancient Mexican Poems (1877), 160.
Oppa icuitl quiqua. Itechpa mitoa: in aquin tla itla oquitemacac, azo itla qualoni, anozo tilmatli: ye no ceppa quitlani = He eats his excrement over again. This is said if someone gives something to another, such as food or a cape. Then he asks for it back. (central Mexico, sixteenth century)
Thelma D. Sullivan, "Nahuatl Proverbs, Conundrums, and Metaphors, Collected by Sahagún," Estudios de Cultura Náhuatl 4 (1963), 102–103.
ocpa = twice (less standard than oppa)
yn oppa = twice
Robert Haskett and Stephanie Wood's notes from Nahuatl sessions with James Lockhart and subsequent research.
itlan xaquj in metlatl, in atl, in venchioaliztli: auh ximotetlacamachiti, maca oppa tinotzalo: iehoatl in pillotl, in velnenotzaliztli, in nezcaliliztli, in tlaimacaxiliztli, in mauhcanemjliztli: auh njman ie iehoatl in iocuxcanemjliztli = Be diligent with the grinding stone, the chocolate, the making of offerings. And be obedient; do not be summoned twice. Nobility is the good doctrine, the way of prudence, the way of reverence, the way of fear, and then the way of peace (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 217.