Its uniqueness to only the Àkúrẹ́ subdialect of Èkìtì and lack of semantic cognates in other Proto-Yoruba branches strongly suggests an inter-dialectal borrowing from SEY forms (likely Oǹdó) meaning "lip." Compare with Ijebu Yoruba ùpọ́nrun, Ìkálẹ̀ Yoruba ùpánrun, Itsekiri ùkpárun, Oǹdó Yoruba ùpánún, The "run" part likely relates to roots for "mouth," see Yoruba ẹrụn, while ùpọ́n means "red." Thus, the word meaning "the red part of the mouth," may have caused the meaning to shift from lip to tongue. Fresco '70 also documents an attested Èkìtì form, ụpọ́nrụn, (which has largely been displaced by ètè (“lip”), which may suggest, along with Olukumi ekpùpẹrún and Ede Nago ɛkpɔ̃, a common inheritance of this root from Proto-Edekiri. Also see Ifè bèbèlè-arũ, which is likely a maintenance of the use of the term "mouth" as the base term compounded to make lip.
Further evidence that this is a borrowing can be seen from the fact that this root does not resemble any other Yoruboid root for tongue, and in fact, a synonym, ụọ́n, a term cognate with other dialectal words for tongue, is still used by not only other Ekiti speakers, but other speakers of the Àkúrẹ́ dialect. In addition, "palarun" does not maintain the /ʊ/ found in the word for mouth, likely suggesting the word was borrowed from a language that did not have /ʊ/ in its sound inventory (which is all the SEY dialects)
Borrowing of body parts between SEY and Àkúrẹ́ with slight semantic shifts is attested, see for example Èkìtì ẹ̀tụ̀pá (“foot”) to Oǹdó ẹ̀tìpá (“thigh”). However this root is also found in Ìjẹ̀bú ọ̀pásẹ̀
pálárun