An Etymological Dictionary of the German Language/Annotated/streng
streng, adjective, ‘strict, severe, stern,’ from Middle High German stręnge, adjective, Old High German stręngi, ‘strong, brave, hard, unfriendly’ (to which the adverb Middle High German strange, Old High German strango, is allied); compare Old Saxon strang, Dutch streng, Anglo-Saxon and English strong, and the equivalent Old Icelandic strangr. Its connection with Strang (strenge, literally ‘tense’) has been already suggested, yet compare also Lettic stringt, ‘to grow tight, withered.’ —