Is it ‘Saint John’, or ‘Sin Junn’? I’ve heard both on various occasions.
If the latter, how did this pronounciation come about? Is it old English?
Probably however Mr./Ms. Saint John tells you to pronounce it is your best bet. But there is indeed an old aristocratic English family who pronounce it “sin-jin”. Another famous example of such a name is Cholmondeley-Marjoribanks, which is pronounced “chumley-marchbanks”.
Speaking of Chumley, does anyone remember a cartoon from the 1960s that had a walrus named Chumley in it it? I imagine he used the phonetic spelling.
I know a St. John who pronounces it as Saint John with equal stress on both syllables. I’ve heard sin-jin in a James Bond movie and thought it the extreme of pretentious snobbery. The issue for me boils down to which of Saint and John should get slightly more emphasis. I vote for John simply because it distinguishes which saint as opposed to which John. But I wouldn’t go to war over either. Sin-jin is as obnoxious as a long-i sound in Smythe. And that was the James Bond pseudonym in whichever movie Patrick Macnee was his valet and they were messing around with Christopher Walken’s horses or something.
Actually, Smythe with a long i was the original Anglo-Saxon pronunciation of Smith (it is related to “smite”, and of course a lot of smiting went on in smithies.)
“Smith” with a short i (“Smeeth”)was a pretentious attempt to Frenchify the pronunciation. But so many people changed the pronunciation that it ceased to be “posh” and just became standard.
The right way to pronounce any name is the way that person wants it pronounced. It’s their name, after all. That is the polite way to do it.
While I do agree with this sentiment, I wince when I hear a pronunciation that violates what I consider commonly accepted rules of orthography, or which seem to be wild and fanciful to the point that someone hearing the name would never guess its spelling.
I give you a few examples:
Tuberville – Auburn University’s head football coach – as if it were Tubberville
Cobble (and other --obb-- names) as if it only had one b
Taliaferro – as if it were Tolliver
Bryce – as if it were Johnson
Hey now, I resemble that.
sinjin 
Tiffany Case (Jill St. John) | James Bond Girls This is how I pronounce it.
And well your should. If it matters at all, I hadn’t noticed your username before now. I’ll try to be nice in the future. 
Tennessee Tuxedo, which I remember fondly from my younger days. There’s a “Best of” DVD out; I wish they would issue the full set.
And isn’t “Saint-John” also used as a first name? In the TV series Airwolf the main character had a (missing) brother named St John (pronounced sin-jin) Hawke.
How do you pronounce “Raymond Luxury-Yacht”?
Just briefly continuing the “Smith” hijack, some names and pronunciations, presented in a jocular fashion:
Working-class: Smith, pron. “Smith”
Middle-class: Smythe, pron. “Smythe”
Upper-class: Smith, pron. “Smythe”
There’s actually quite a lot of truth in that.
“A View to a Kill”
Indeed, I had even looked it up to be sure how to spell Steed’s name. I watched it within the past couple of months as part of the James Bond collection on Comcast On Demand, along with every other Bond movie they had. Took several days.
I just didn’t think its title was all that significant for the topic at hand, aside from the St. John reference. But thanks for providing it in case others couldn’t quite recall which movie.
Hello what???
Throatwobbler Mangrove, of course. How else would you pronounce it?
You caught that did you? It was a joke. But there are some names I’ve encountered that are spelled virtually no way close to how they’re pronounced. And when my wife and I have this discussion, it’s her position that there’s no such thing as a “mispronounced” name: it’s the owner’s right to say it however they want. I tend to disagree. Some things are just plain wrong.
You lost me. How would you pronounce Coble (one b) vs. Cobble (two bs)?
Coble = Koh-bull
Cobble = Cobb-bull (Cobb as in Ty Cobb and corncob)