My thought wasn’t so much nomadic at the time of TOS as nomadic in origin. It was based in something written by Jerome Bixby or John Meredyth Lucas, or maybe Gene Coon, that included the background about the Klingons being poor and deprived of resources, and being forced outward just to survive. Mara says as much in “Day of the Dove”: “We have always fought. We must. We are hunters, Captain, tracking and taking what we need. There are poor planets in the Klingon systems, we must push outward if we are to survive.”