It appears that there is no etymological information available about this town, based on the fact that the geography of this region was studied in depth by Charles J. Tissot, and none of the evidence about its name is etymological in nature. In his Géographie Comparée de la province Romaine d'Afrique, Tissot says the following:
We also owe Mr. Dewulf for a second, no less interesting inscription,
which definitively fixes Kasr Sbehi as the location of Gasaupala from
Peutinger's table. We reproduce it here:
This text also gives us the true spelling of the name that Peutinger's
table, Antonin's itinerary and the Notice of the Churches of Africa
write Gazaupala, Gazaufula and Gazaufala. (Géographie Comparée de la
province Romaine d'Afrique, pg 418)
Here's the itinerary and table he refers to:
It might also be of interest that an alternate spelling of this town is Gazophyla, and it's mentioned in Procopius' The Vandal Wars § 4.15.52:
ὃς ἐπεὶ ἐν χωρίῳ Γαζοφύλοις, δυοῖν μάλιστα ἡμέραιν ὁδῷ Κωνσταντίνης
ἀπέχοντι, Στότζαν ξὺν ὀλίγοις τισὶν ἤκουσεν εἶναι, προτερῆσαι πρὶν
τοὺς στασιώτας ἅπαντας ξυλλεγῆναι βουλόμενος, κατὰ τάχος ἐπ̓ αὐτοὺς
ἐπῆγε τὸ στράτευμα.
He, therefore, upon hearing that Stotzas with some few men was in a
place called Gazophyla, about two days' journey distant from
Constantina, wished to anticipate the gathering of all the mutineers,
and led his army swiftly against them.
This town is also mentioned by Augustine in De Baptismo Contra Donatistas § 7.40.78:
Salvianus a Gazaufala dixit: Haereticos nihil habere constat; et ideo ad nos veniunt, ut possint accipere quod non habebant.
Salvianus of Gazaufala said: "It is generally known that heretics have
nothing; and therefore they come to us, that they may receive what
previously they did not have.
In a footnote, Philip Schaff affirms that these names refer to the same place:
Gazaufala (Gazophyla) was in ecclesiastical province of Numidia.