Further random cultural notes:

I would like to point out that the yobisute style of speaking occurs in languages other than Japanese, although it's most explicit there. It had a prominent place in English up until, oh, fifty years ago or so.

The BBC's Sherlock plays with it in the modernization; the protagonists call each other 'Sherlock' and 'John' in the modern day, because this is the appropriate localization (...chronolization?) of the two of them calling one another 'Holmes' and 'Watson' a century prior. Strangers address them both with titles, as 'Mr Holmes' and 'Dr Watson', to pay them the proper respect. First names are only for family and lovers -- the Holmes brothers, note, call one another 'Sherlock' and 'Mycroft' -- but the precise relationship of the detective and his doctor is more in the nature of a close friendship than anything involving professional distance. Hence, dropped titles as a sign of intimacy between social equals.

In a business setting, where the hierarchy was formally outlined, yobisute was generally a sign that you were on good terms with someone who was your equal or slightly-inferior in the organizational structure. A company vice president in the '40s or '50s might buzz his secretary to 'send Jenkins in', Jenkins presumably being one of the diligent workers he supervises, but the secretary would be too far down the totem pole (and too female) for such distance to be dropped, and would still be addressed as 'Miss Smith'.

Yobisute-style was also once used in upper-class English schools and universities, especially among boys, where schoolmates would address one another casually by their surnames. I'm not sure how much this survives today, inasmuch as I've never personally been to an upper-class English school, but it's still referred to in jest by comedians like Stephen Fry, who have been there, and who like to poke fun at social institutions. There may be a generational break in there somewhere. Benedict Cumberbatch also has a lot of very expensive schooling in his background, and he's quite casual with his castmates.

The practice also exists in English-language journalistic style, which is usually what I try to write in when I'm doing profiles. Full name the first time someone is mentioned, surname-only thereafter. The consistency with which it's followed is directly related to the respectability of the publication -- tabloids will often refer to celebrities by their first name or nicknames, particularly women, which annoys me to no end.

Other languages involve still other forms of address that don't have exact English equivalents. My Arabic teacher was a Russian lady from Moscow. I think I was the only one who ever called her by her first name plus patronym; other people used the standard English "Mrs. Surname" or just used her first name, which is relatively common in the US with university instructors who don't hold a doctorate, but given+patronym is how you address a Russian person who is leading your lecture goddamnit, and my brain really would not let me do it any other way. On the other hand, anyone who survived to the third year of our Japanese classes ended up calling the teacher (Firstname)-sensei, which probably horrified any actual Japanese people who heard it, but which pleased Sensei to no end -- she made a much better American woman than she ever did a Japanese girl.

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