An Etymological Dictionary of the German Language/Herr
Herr, m., ‘master, lord, gentleman, sir,’ from MidHG. hërre (hêre), m., OHG. hē̆rro (hêro), m.; comp. OSax. hêrro, Du. heer, OFris. hêra, ‘lord’; prop. a comparative of hehr (OHG. hêr), in Goth. *hairiza. In the OHG. period this origin was still recognised, as is seen by OHG. hêrero, ‘lord’ (see herrschen). Since the orig. meaning of the adj. hehr was ‘venerable,’ Herr seems to have originated in the relation of the dependants to their master (comp. AS. hlaford, ‘bread guardian,’ under Laib), and was used chiefly as a term of address (see Jünger). Comp. in Rom. the words used in the same sense from Lat. senior, viz., Ital. signore, Fr. seigneur. Herr is orig. native to Germany, but in the form hearra it found is way at a very early period (about the 9th cent.) from the German lowlands to England, and later to Scandinavia (ModSwed. herre, ‘master’). In ModHG. only a fem. Herrin has been formed from Herr (as in Ital. signora from signore). The older language used Frau, Herr having supplanted the earlier frô (see under frohn).