An Etymological Dictionary of the German Language/Annotated/Mensch
Mensch, masculine and neuter, from the equivalent Middle High German męnsch, męnsche, masculine and neuter, ‘man, person, fellow,’ Old High German męnnisco, mannisco, masculine; compare Old Saxon męnnisco, Dutch mensch, ‘person.’ Simply a West Teutonic form, properly an adjective used as a substantive, hence ‘humanus’ for ‘homo.’ The adjective on which it is based is derived with the suffix iska (High German isch) from mann-, ‘homo’; Gothic mannisks, Old Icelandic mennskr, Anglo-Saxon, Old Saxon, and Old High German męnnisc, ‘humanus, human’ (compare further Anglo-Saxon męnnesc, ‘humanity’); compare manušýa as an adjective ‘human,’ and as masculine substantive ‘man,’ with Sanscrit mánu, mánus-, ‘man’ (see further under Mann). — Mensch in the neuter gender appears even in Middle High German, and was used till the 17th century without any contemptuous meaning; the neuter was generally applied to female servants, but that signification became obsolete in the last century, and a moral sense was attached to the word.