Excerpted from Lingo: Around Europe in Sixty Languages by Gaston Dorren. Out now from Atlantic Monthly Press.

The year 1967 was the height of the hippie era. The Beatles, with “Lucy in the Sky With Diamonds,” are singing the praises of LSD. And, almost equally shocking, a top Swedish executive is calling for unprecedented levels of informality. Bror Rexed, the incoming director-general of the Medicinalstyrelse (Public Health Board), announces that he intends to address all employees by their first names and would like them to do the same for him. And he gets his way.

So, ever since July 3, 1967, Rexed’s name (particularly his surname, ironically enough) has been linked to the du-reform. Du, in Swedish as in German, is the informal version of the English “you.” French has the equivalent tu and English, between the 13th and 18th centuries, had thou. Which is not to say this was all Rexed’s doing. There had been signs already that the tide of public opinion was turning, and a short time later even Prime Minister Olof Palme endorsed the new trend: upon taking office in 1969, he publicly dealt with journalists on a first-name-and-du basis. Nevertheless, in Sweden’s collective memory, Rexed’s announcement has remained the symbolic turning point.

It was a turning point that was overdue, because the rules of linguistic etiquette that had been in use until then were extremely complex. The most formal variant consisted of three parts: herr (“Mr.”) or fru (“Mrs.”), followed by the person’s societal position (such as doctor, count, or lieutenant), and finally the surname. If Rexed had not taken his stand, his employees would have had to call him Herr Generaldirektör Rexed. And not as a term of address, mind you, as we might say “Mr. Rexed,” but instead of “you”: “Would Herr Generaldirektör Rexed like a biscuit?”

For someone less senior, herr or fru could be omitted: “Would Accountant Persson mind sending the invoices this afternoon?” Another variant was the use of surname only. That, for example, was how a boss would address his subordinates: “Did Almquist have a good weekend?” In communication with maids and servants, last names gave way to first names: “Has Agatha emptied the chamber pots?” And among the lower classes and in the country, the typical terms were simply he and, to a lesser extent, she: “When will he be harvesting the rye, then?” Note that he here in fact means you.

All these niceties—and there were many more, such as using “mother” when addressing an older woman (as in, “Would mother Brigitta care for a cup of coffee?”)—called for real precision. Mistakes were easily made, superiors quick to take offence. Swedes had to keep careful tabs on whose position or rank had changed, so as not to address as “lieutenant” the newly promoted captain. (If ever there was a need for LinkedIn … ) Only spouses and lovers had it easy: They could simply call each other du. So could friends, but not until they had shared a so-called “du-drink.” These exceptions aside, du was acceptable with children only, and of course with people for whom one had no respect.

Little wonder the Swedes had long toyed with the idea of reform. In the early 20th century the word ni, previously used only as the plural of you, had enjoyed a measure of popularity as a formal singular, equivalent to vous in French. However, because its use aroused the suggestion that the addressee had no title, it was seen as insufficiently respectful. Another strategy was to avoid second-person pronouns entirely, by invoking cumbersome formulations such as “Would a biscuit be permitted?” instead of “Would you like a biscuit?” But this was unwieldy and even came to be seen as impolite.

When the revolution came, it came fast. In the early ’60s, prudence still reigned. But by the close of the decade, even the prime minister had been du’d, like anyone off the street. Only the royal family remained out of range.

And now? Nobody longs for a return to the old system, but the informal pronoun, du, seems to be losing ground to ni, its more formal counterpart. Gradually, these two words have come to symbolize opposing visions of society. Progressive Swedes do not like ni. It points to “the return of the class society,” writes the former social-democratic councillor Britta Sethson on her blog, Nyabrittas. As she sees it, this practice has become mandatory in shops solely because “employees should be made to feel, in their very bones, that they are just a little inferior.”

Excerpted from Lingo: Around Europe in Sixty Languages by Gaston Dorren. © 2015 by Gaston Dorren; first published in Great Britain in 2014 by Profile Books; reprinted with the permission of the publisher, Atlantic Monthly Press.