An Etymological Dictionary of the German Language/Annotated/langsam
Modern High German langsam, adjective, ‘slow,’ is one of the earliest forms ending in sam (in Gothic only lustusams, ‘delightful, longed for’); Anglo-Saxon longsum, ‘tedious, continuous,’ Old Saxon langsam. In Old High German, besides langsam, ‘lasting a long time,’ there exists a form langseimi, ‘lingering,’ and in Middle High German lancsam, adjective and adverb, ‘slow,’ as well as lancseime, ‘lingering, slow’; in Modern High German langseim became obsolete, and its meaning has been transferred to langsam.