An Etymological Dictionary of the German Language/Annotated/lehren
lehren, verb, ‘to teach,’ from Middle High German and Old High German lêren, ‘to instruct, teach, make one acquainted with,’ sometimes also ‘to learn’; corresponding to Dutch leeren, Anglo-Saxon lœ̂ran (whence Old Icelandic lœ̂ra is borrowed), Gothic laisjan, ‘to teach.’ A common Teutonic verb with the primitive meaning ‘to cause to know’; laisjan is the factitive of a preterite present lais, ‘I know,’ preserved in Gothic only. In German and English only a participle derivative was retained, which was probably represented in Gothic by *lisnan or *liznan; compare lernen. Allied also to Gothic leis, ‘knowing,’ leisei, ‘knowledge,’ in lubja-leis, -leisei, ‘skilled in poisons, witchcraft.’ We have data for assuming that Gothic lais, ‘I know,’ is based on a primary meaning ‘I have experienced,’ for the stem lis of lehren and lernen appears also in Gleise and leisten in the old sense of ‘to go,’ with which Latin lîra, ‘furrow,’ and its derivative delîrare (literally ‘to slip away from’) are connected, as well as Old Slovenian lěcha, ‘ridge (of a furrow),’ mentioned under Gleise; compare leisten. —