The usually agreed-upon (Salmons: 325, Besch et al.: 2599; Simon: 94) first instance of ir being used in the more formal sense – i.e. with some politesse behind it rather than as a straightforward plural – can be found in Otfrid’s letter to Salomo, Bishop of Constance, in which he writes:
(‘whether you find something here worthy of reading’)
Otfrid is clearly writing to only one individual, so this can only be ir in the polite, formal sense. The usage of du and ir in this manner continues into MHG, where the main thing to note is inconsistent application depending on source and subject matter. Besch and Wolf identify “Geistliche Erzählliteratur” and “Spielmannsepen” as retaining the ubiquity of du to a greater extent than more classical forms and “Erzählstoffe aus lat. oder französischen Vorlagen”, the latter having possessed “eine starke Hinwendung zum Höflichkeitspronomen ir”.
In other words, the more courtly society that was developing in German-speaking areas – again, predominantly due to French influence – lent itself to a certain formality and social hierarchy which could be promoted through the judicious use of pronouns of address. We might note the link between Hof ‘court’ and höv-esch (later höflich) ‘courtly’, later ‘polite, courteous’; appropriately the word was taken from the French adjective curt-eisie, itself a reflection of the Francophile nature of the German courtly world. This is so particularly during the period of the ‘höfische Dichtersprache’, during which the du/ir model is a division between gentry and commoners. Ir was meant for “Adel, Geistlichkeit, Regierende, überhaupt für alles Herausgehobene” whilst du was for “das Volk”; two nobles would therefore address one another as ir and a peasant as du, while the peasant would address the nobles as ir but any fellow peasant as du. To call someone else du when it was commonly assumed that they were owed the respect of being addressed as ir seems to have been an aggressively offensive act, as with the dying Hagen to Kriemhild (shortly before he calls her a ‘she-devil’) in the Nibelungenlied, strophe 2370: du hâst iz nâch dînem willen z’einem ende brâht [my emphasis]. The link between formality/informality and familial/workplace situations that we know today is a later development of this nobility/serf distinction, although even as early as Wolfram von Eschenbach’s Parzival (the first quarter of the 13th century) we can find an instance of Feirefiz inviting Parzival to call him du because they are half-brothers (i.e. they are family and so can address each other in a more familiar manner): du solt niht mêre irzen mich, he says, also clearly indicating that irzen and presumably duzen were in use as verbs by this time. But Parzival refuses until he is of the same station as Feirefiz, indicating that social position held immense sway.
As Nübling observes, “viele Sprachen machen innerhalb der Anrede eine Unterscheidung zwischen höflich-respektvollen und normalen Anredemitteln”. Yet of all the European languages, it was German in particular which went through quite the subtle variations in form of address – especially during the Early New High German. In the 16th and 17th centuries, distinguishing people by personal pronoun reached its height, most notably in the form of er and sie – traditionally third person pronouns – being repurposed as second person pronouns of greater respect in the manner of the Spanish usted stemming from vuestra merced, ‘Your Grace’ (where the er or sie would be anaphorical for a title: ‘Gebe der Herr mir den Rock’, for instance). This has its parallel in English ‘Would His Grace like to step this way’ etc. but was much more widespread; as C.J. Wells explains, this was most brilliantly portrayed by Andreas Gryphius
In 1789 the French Revolution fundamentally alters the courtly prevalence of vous that had remained in the French language since its early medieval days: suddenly vous is a filthy aristocratic word, expressing all manner of decadence, and to be avoided utterly; a 1793 decree insisted that everyone must “tutoyer sans distinction”. Other levelling revolutionary movements, in which the principles of liberté, égalité, fraternité are embraced – or Brüderschaft, for instance, or the English comrades-in-arms – include the 1848 revolutions, and, albeit much later and in living memory, the 1968 student movements, far more marked in Germany and France than they were in the UK. The net result of each of these generational movements, in their day, was as levellers that helped erode social distinctions and hierarchies (much as the two World Wars, in particular, also did in the UK); the emphasis on equality and justice made it much more acceptable to address one another as du, especially among young people of the same age: it has the ring of solidarity to it.
The pronoun Sie, however, has proved resilient since the ENHG years: until the latter half of the 20th century, it was “zwingend erforderlich, und unabgesprochenes Duzen von Erwachsenen konnte (mindestens bis zu den 1968er Jahren) mit Geldstrafen gerichtlich geahndet werden”. In modern usage, Sie is used to express what Nübling calls “negative Höflichkeit”, in which negativ does not have a pejorative meaning; rather, the distinction is made between politeness which grants another person space, respect and distance, and positive Höflichkeit”, which is more focussed on compliments and familiarity. Thus we would do better to refer to respect rather than politeness, since it is not as though du is an impolite word (though it can have an undertone of that in the modern era if used as a deliberately provocative word to people of a lower social station or as a non-discriminate catch-all for all non-Europeans). Besch and Wolf’s four variables for distinguishing between people in terms of pronouns of address – age, gender, social position and situation – have been relevant to varying degrees throughout German’s history. In more class-conscious centuries gone by, for instance, social position might have been more important than today, though its relevance is not completely gone; whereas situation is of more importance in the modern world of consumerism and “customer is king”, in which a waiter or waitress will reliably use Sie to any customer over the age of 16. The Kinder-Du and the Erwachsenen-Sie remain in place, whilst MHG honorifics like herre and frôuwe have become the everyday words Herr and Frau, much as the English gentleman has come to mean a man who behaves in a chivalrous manner (though we might see that, too, as an outdated term!) rather than a descriptive word for a man with estates and a title to his name. The fact remains, however, that there are times and occasions when the pronoun of address one chooses in German is immensely important: “je formeller eine Situation, umso strikter die Regeln der Anrede”. The Du-Expansion since the infamous days of 1968 may seem ongoing and irrevocable, but we are not quite in the “Zeitalter des Duzens” just yet.