Penny (2002) notes that cansar is a particularly interesting archaism in Spanish. Because the Romans entered the Iberian peninsula and began the process of Latinization at such an early date (~3rd cent. BCE), the Latin dialect of the peninsula inherited a number of archaic vocabulary terms. Cansar is one such item, not found in Latin literature after the 2nd cent. BCE but evidently preserved in the dialect of Latin to become Spanish.

Originally canare meant "to sing" while cantare, with -tare added, was more forceful. Over time the impact of cantare was lost and began to match the meaning of canare. Thus, canare was replaced by cantare. When later speakers wanted to give force and frequency to the verb, they once again added -tare to cantare to form cantitare - unaware that their ancestors had created cantare from canare to fulfill that purpose. Cantitare has not survived in Spanish.

The Proto-Indo-European root behind cantar "prevailed only in Italic and Celtic, where it is associated with charms and spells as well as poetry. ...Latin cano, canto, cantus, carmen < *can-men, all of magical incantations as well as of singing in general." ~ M. West, Indo-European Poetry and Myth (2007)

Note the variation between *ka- and *ga- in Celtic (cf. Old Irish caera "sheep" and gabor "roebuck"). Additionally, note the variation between *-b- in Celtic and *-p- in Greek and Latin. There is no way to explain the interchange between *ka- ~ *ga- and *-p- and *-b- from within Indo-European. The words must come from a non-Indo-European source or sources.

Only Western Romance languages preserved the Latin word cara while Eastern Romance preferred the Vulgar Latin term *facia (also in Modern Spanish as faz).