Principal English Translation: 

something bent, twisted ("col" seems to be a root for many terms with this meaning, although colli usually translates as grandfather, grandparents, forebears, or ancestors)

Attestations from sources in English: 

cōlli = "Lit., that which is bent, crooked, or twisted (see cōltic)."
John Bierhorst, A Nahuatl-English Dictionary and Concordance to the Cantares Mexicanos, 1985, 91.

"The curved mountain references Culhuacan phonetically and ideographically. The curvature of the mountain's peak evokes the Nahuatl root 'col,' something twisted,' and its derivatives: for example, 'colihui,' to bend'; 'coloa,' 'to bend or twist something'; or 'colli,' something 'bent or twisted.'"
Eduardo de J. Douglas, In the Palace of Nezahualcoyotl: Painting Manuscripts, Writing the Pre-Hispanic Past in Early Colonial Period Tetzcoco, Mexico (Austin: University of Texas Press, 2010), 212 n65.