An Etymological Dictionary of the German Language/Annotated/irre
irre, adjective, ‘in error, astray, insane, confused,’ from the equivalent Middle High German irre, Old High German irri, adjective (Old High German also ‘provoked’); corresponding to Anglo-Saxon yrre, ‘provoked, angry.’ Allied to Gothic airzeis, ‘astray, misled’ (High German rr equal to Gothic rz). Anger was regarded as an aberration of mind (compare also Latin delirare, allied to lira, ‘furrow,’ properly ‘rut’). The root ers appears also in Latin errare, ‘to go astray’ (for *ersare), error, ‘mistake’ (for *ersor); allied also to Sanscrit irasy, ‘to behave violently, be angry’?. —