The only free and comprehensive online etymological dictionary of the Spanish language
fallar (Verb) "to fail"

From Latin fallare "to deceive," "to mistake." From Proto-Italic *faln-e/o- 'id.' From Proto-Indo-European *sgwhel-n- "to stumble."

According to Tibón (1988), also the origin of the surname de Falla, when the so-named is not from Valencia, but the origin account is passed over without comment.

Romance: Western Vulgar Latin: Portuguese falhar, French faillir, Italian fallare

Indo-European: Hellenic: Ancient Greek σφάλλομαι (shállomai) "to fall," "to be ruined;" Armenian: sxalem "to fail;" Indo-Iranian: Sanskrit skhalate "to stumble," Middle Persian škarwīdan 'id.'