Wikipedia's own History section states there is no record of the pocket pita in ancient texts or medieval Arab cookbooks and that food historians such as Charles Perry and Gil Marks consider it "likely a later development," with no period or century named.
What would resolve this A food-history source naming the period or region where the steam-puffed pocket technique was first documented, as distinct from the much older prehistoric Near Eastern flatbread lineage.
Openfood historyPita (Wikipedia)