Etymology
In many cases, from German Klingen, via Russian Клинген (Klingen) (many bearers in 1900s US censuses are recorded as being from Russia). Compare the various spellings of the related surname Klingon Smith (more commonly Klingensmith, Klingenschmitt, Klingenschmidt).
Definitions & examples from Wiktionary (CC BY-SA 3.0).