Rhentanoi

The Narentines was a South Slavic tribe that occupied an area of southern Dalmatia centered at the river Neretva (Narenta), active in the 9th and 10th centuries, noted as pirates on the Adriatic. Named Narentani in Venetian sources, Greek sources call them Paganoi, "pagans", as they were for long pagan, in a time when neighbouring tribes were Christianized. The tribe were fierce enemies of the Republic of Venice, having attacked Venetian merchants and clergy passing on the Adriatic, and even raided close to Venice itself, as well as defeated the Doge several times. Venetian–Narentine peace treaties did not last long, as the Narentines quickly returned to piracy. They were finally defeated in a Venetian crackdown at the turn of the 10th century and disappeared from sources by the 11th century.

The word Narentine is a demonym derived from the local Neretva river (Latin: Narenta). In the 10th-century De Administrando Imperio (DAI) of Byzantine emperor Constantine VII Porphyrogenitus (r. 913–959), the tribe is called Paganoi (Greek: Παγανοὶ, Παγανοἰ), and their polity Pagania (Παγανὶα, Παγανἰα), in Greek, while also noting that in Latin they are called Arentanoi (Αρεντανοἰ) and their polity Arenta (Αρεντα). The Pagani are so called because they did not accept baptism at the time when all the Croats were baptized."Venetian sources (John the Deacon) used the geographical term Narentani (as in princeps Narentanorum,Narrentanos Sclavos) and Slavic ethnonym (Sclavi) to refer to the people. In Croatian, the tribal name is rendered as Neretljani (Неретљани) and Pagani (Пагани), while the polity mostly as Paganija (Паганија).

...
Wikipedia