Borrowed from Proto-Germanic *kunjan. The meaning changed from "family, clan" to "noble family, family honour" and finally to "honour". See kön.
It is unlikely to change from the generic "family" to the specific "noble family" while likely from "noble family" to "honour" which is simply a metonym. The proper noun Xerox gave way to the common xerox. Such may be barely vice versa.
Suppose that the Huns proper were a noble and honorable tribe indeed, while other tribes called themselves Huns more often than not, whether to be feared or honored. They traditionally practiced the artificial cranial deformation, and their subjects followed suit. Most Germanic kings may have been Hunnic or Hunnish, hence the name whence Old English cyning or Old Saxon kuning literally "Hunnic or Hun child" akin to Kölsch Künnisch "Hunnish" cf. Proto-Germanic *kuningaz. Please, correct me if my view is too mistaken.