What I'm referring to is that STID specified "Ketha" to be the name of a political division in addition to a physical geographic feature.
I take it you're going by Memory Alpha, which only cites STID in its "Ketha Province" article and describes "Once More Unto the Breach" as referring only to the Ketha lowlands. But Martok's actual line from the episode was, "When I was a boy, my family still lived in the lowlands of Ketha Province." So DS9 did, in fact, establish that it was a political division.