Definition - What does Pali mean?
Pali is an ancient language that is used in some Buddhist texts. It is a middle Indo-Aryan language similar to Sanskrit, but the latter is an older language. Despite many similarities between the languages, Pali is not believed to be derived from Sanskrit. Its origins are not definitively known, but some believe it evolved from a language used by the Buddha (a Magadhi dialect).
It is thought that the Buddha did not want to use Sanskrit because it was the language of the educated. Instead, he encouraged his disciples to use their local dialects.
Yogapedia explains Pali
As a literary language, Pali faded out in India in about the 14th century, but was still evident elsewhere until the 18th century. Today, Pali is chanted as part of Buddhist rituals and is studied in order to read and understand Buddhist scriptures.
More specifically, Pali is the language of early Theravada Buddhist texts, is the language of some Hindu religious texts, and is — as the name suggests — the language of the Pali Canon, or Tipitaka. The Pali Canon is the complete collection of Theravada scriptures in the language in which it was composed.