mongrel: [15] The etymological notion underlying mongrel is of a ‘mixture’. For the word goes back ultimately to the prehistoric Germanic base *mong- ‘mix’, which also produced English among and mingle [14]. => among, mingle[mongrel etymology, mongrel origin, 英语词源]
late 15c., "mixed-breed dog," from obsolete mong "mixture," from Old English gemong "mingling" (base of among), from Proto-Germanic *mangjan "to knead together" (see mingle). With pejorative suffix -rel. Meaning "person not of pure race" is from 1540s. As an adjective from 1570s.