Tetrarch Varis Sul of the Paqu village met with Commander Sisko in 2369 to discuss a dispute between her village and the Navot, lead by Woban. She took over the title from her father after his death. (DS9: "The Storyteller")
It is unclear if Woban had the same title as Varis, as he did not use a title. The prefix tetra- or tetr- (as in tetrahedron) means four, while -arch (as in matriarch) means ruler. Thus, a tetrarchy would presumably mean rule by four people, or possibly a collaborative government run by the Paqu, Navot, and two other villages. The exact meaning of the word is unclear; it is possible that the writers simply thought it sounded nice and decided to use it.
Later episodes did not mention or use this title, and it is worth noting that the inner workings of the Bajoran people and their government had not entirely been established when "The Storyteller" was filmed. One could hypothesize that, as the newly-formed Bajoran Provisional Government became more organized, it unified the planet and removed the need for seemingly autonomous villages such as the Paqu and Navot. Thus, "Tetrarch" might have been a temporary title invented in the interrim.