Sciallà is a Neapolitan slang term that means "chill out" or "relax." It's an informal and very expressive word that captures a laid-back, carefree attitude.
In the context of the song, it's used as an exclamation, encouraging a sense of calm and letting go of worries, perfectly embodying the song's relaxed, groovy vibe. It's not a standard Italian word, making it unique and interesting for learners.
Sciallà is Neapolitan for taking it easy, and Nu Genea build the whole song out of that one shrug. It opens on someone being pestered: "Ma che r'è? Che r'è? / 'O vaje truvann 'a me" [What is it? What is it? / You come looking for it from me]. His answer is to refuse the errand outright and say so plainly, "Ij penzo a mme, mme, mme" [I think about me, me, me].
The chorus turns that refusal physical, and it is funnier than it sounds. "A chi me vo' tucca', fa capa e muro" [Whoever wants to touch me can bang his head on the wall] and "A chi me vo' scuccia', care iss sulo" [Whoever wants to bother me falls all by himself] work the same way: he does nothing at all, and the other person hurts himself. Under that sits a fatalism the song keeps returning to, "Ma che sarrà, sarrà, sarrà che sarrà" [But what will be, will be, will be what will be], with its reason attached: "si s'arape 'nu purtone, 'a porta se chiurarrà" [if a big door opens, the door will close]. One thing arrives, another shuts behind it, so there is one way left to live. The word carrying that is aller, local slang for carefree, and the whole track is built to sit inside it.