The Akkadian verb cannot be separated from Sab.
hfs₂ḥ ‘to cause to rejoice’, Gez.
tafaŝŝəḥa ‘to rejoice, to be glad, to be comforted’, Tna.
tafaŝŝəḥe ‘to rejoice, to be happy’. Since pesû is attested only once in Malku, one would be tempted to regard it as a WS (loan)word, but its phonetic shape (lack of the guttural, e-coloring) does not favour such a possibility, rather suggesting an autochthonous Akkadian word.