pi.

pi. nitla. (pret. onitlapic.) pelar, o sacar de rayz los pelos, o coger yeruas sin arrancar las rayzes dellas.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 81r. col. 2. Thanks to Joe Campbell for providing the transcription.

PĪ vt: pret: PĪC to gather plants without disturbing the roots, to pluck something / pelar o sacar de raíz los pelos o coger yerbas sin arrancar las raíces de las (M) The evidence for the vowel of this verb being long is circumstantial. The verb is abundantly attested in C but not in the modern sources, which have only CUI and PEHPEN(A). C does not mark the vowel long in several attestations of the preterit but does consistently mark it long in causative PĪLTIĀ. This is weak evidence, because there is some variation over verbs in general between short and lengthened vowels before -LTIĀ. For CUI there is more evidence of a short stem vowel, but its attested causative is nonetheless CUĪLTIĀ. In the attested applicative form of redupli-cated PIHPĪ T has the reflex of a short vowel before –LIĀ. See PIY(A), PĪQU(I). PĪHUA nonact. PĪ. PĪLTIĀ caus. PĪ.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 193.