Principal English Translation:
something sour (see Molina); might also be used for unripe, green fruit
Alonso de Molina:
xococ. cosa agra.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 160v. col. 1. Thanks to Joe Campbell for providing the transcription.
Frances Karttunen:
XOCOC something sour / cosa agria (M) [(1)Tp.246, (2)Zp.6,229]. In both attestations in Z the vowel of the second syllable is marked long, but it is short in T. See XOCO-TL.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 329.
Attestations from sources in English:
xocōc = "sour (like the xocotl fruit)"
Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 112.
yn Maria ycnocihuatl xocoatolnamacac ynin ynamic yn franco tlatzonqui Sastre catca nican chaneque ytepotzco yn teopantli = María, a widow and seller of bitter atole, died. She was spouse of the late Francisco, a tailor, and they lived here behind the church (central Mexico, 1613)
Annals of His Time: Don Domingo de San Antón Muñón Chimalpahin Quauhtlehuanitzin, James Lockhart, Susan Schroeder, and Doris Namala, eds. and transl. (Stanford: Stanford University Press, 2006), 250–1.
Attestations from sources in Spanish:
ahmo quiquiz in xochiqualli xococ, ahmo no quiconiz coztic octli = no lo tomará la fruta cruda no también lo tomará amarillo pulque (centro de México, s. XVIII)
Neville Stiles, Jeff Burnham, James Nauman, "Los concejos médicos del Dr. Bartolache sobre las pastillas de fierro: Un documento colonial en el náhuatl del siglo XVIII," Estudios de Cultural Náhuatl 19 (1989), 269–287, ver página 280.