-cel.

Headword: 
-cel.
Principal English Translation: 

someone or something alone, by oneself or itself, only, unique

James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 213.

Orthographic Variants: 
-cēl
IPAspelling: 
-sel
Frances Karttunen: 

-CEL necessarily bound form; pl: -TIN alone / solo.... solos (C) When bound with a possessive prefix, this means ‘oneself alone’; NOCĒL ‘I alone’, TOCĒLTIN ‘we alone’. It can also be incorporated into verbs to convey exclusivity. Z has the variant form CĒLTI. See CĒ, CEM
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 28.

Lockhart’s Nahuatl as Written: 

necessarily partially possessed indefinite pronoun. can have a pl. -cēltin.
James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 213.

Attestations from sources in English: 

Ca çan moceltzin in ticmocaquitia in totlatol in nicā ycuiliuhtoc = Only you yourself heed our words here written down. (central Mexico, early seventeenth century)
Codex Chimalpahin: Society and Politics in Mexico Tenochtitlan, Tlatelolco, Culhuacan, and Other Nahuatl Altepetl in Central Mexico; The Nahuatl and Spanish Annals and Accounts Collected and Recorded by don Domingo de San Antón Muñón Chimalpahin Quauhtlehuanitzin, eds. and transl. Arthur J. O. Anderson and Susan Schroeder (Norman: University of Oklahoma Press, 1997), vol. 2, 206–207.

cel = sole, only
Daniel Garrison Brinton, Ancient Nahuatl Poetry: Containing the Nahuatl Text of XXVII Ancient Mexican Poems (1887), 151.