Was at the bar (am American) a few nights ago and a guy from Ireland who is visiting his wife’s family comes in. Me and my buddies are chatting with him, making a few jokes, and he is laughing quite a bit and calls us (whenever we make a joke) “Legend”. In the US, legend is for someone extraordinary for a while and would never be used for someone who is just making funny jokes.
So are you saying that in your dialect a frown can mean -
(a) furrowed brow only, signifying displeasure or concentration;
or
(b) downturned mouth (with furrowed brow?) signifying sadness.
I think it’s probably the entirety of (b) - both the facial expression and the indication of sadness - that are not part of the range of meaning of the word for Brits and (per comments above) some Americans.
In that context, I think he’s using the word as you might say “awesome” or “fantastic”. In other words, more about the joke being great than about the person.
I’m 56 - when I was a kid, I thought of it primarily as a mouth expression, but I learned later, the whole face and forehead are significant in a real frown.
It’s just like how a smile is not just with the mouth, but with the eyes. When someone fakes a smile with just his mouth (think Trump’s Twitter pic), you can tell it’s not genuine because they eyes aren’t smiling as well.
If you asked someone to frown, they may just do an inverted smile with their mouth, but then it wouldn’t look authentic.
What is the trajectory of the American slang “sick”? I heard it a few years ago (as an expression of approval, similar to “cool” or “awesome”), but I have not been around many young people lately, so I get the impression that that usage has declined.
Well he peppered it with “You’re legend” or “He’s legend” (to be fair, he was fairly drunk too). Though I also guess we Americans wouldn’t use the term for awesome and fantastic either.
To be honest, I’ve never heard (a) as an East Coast American. Frown has always been a downturned mouth to me.
I hear it much less than I used. Whenever I do hear it, it makes me think of the 90s. I hear “cool” or “lit” much more often.
In my dialect, as I’ve always known it, it means “b.” Just like the sad face emoticon 
here, if you hover over it, the pop-up text says “frown.” The expression may also consist of scrunching up other parts of the face, but I pretty much solely associate it with the mouth, like in the phrase that was mentioned “turn that frown upside down!”
ETA: What I was saying is that if you interpret “frown” as A), then that type of “frown” denotes displeasure/discomfort/confusion/concentration and not (usually) sadness. If I were to ask someone “why the frown?” I would be asking something like why are you looking sad. I would assume in your dialect, “why the frown” would mean something like “what is concerning you?” or something to that effect? I might say something like “why the serious look?” or something like that, rather than “why the frown?” if it’s a look of intense concentration or consternation I see.
The strangest part of the frown discovery to me was that some of the British commenters on the SBACL blog made the claim that a downturned mouth is not a natural human facial expression! It’s like the lack of a word for the expression made them unable to see it. Very strange.
This is fairly new, in geological terms. 
My grandparents, and even my father to some extent, might call any group of musicians an orchestra. (Frequently in the sense of a group that got together to play at a dance)
(They had zero experience with Spanish, or with any languages but English.)
Maybe he’s using “legend” a bit more literally - “That one deserves to be a famous story everyone has heard of!” - along with a little bit of the drunk person’s tendency to be disinhibited and exaggerate, it makes some sense.
“Legend” can be used as a generally expression of gratitude or coolness in UK and I assume Hiberno-English. I could swear I hear it in Ricky Gervais’s voice from The Office. Definition #10 here on urbandictionary is how I’ve heard it:
Or, for those who don’t like Urbandictionary for whatever reason, here’s BBC Learning English:
Exactly. Like the Electric Light Orchestra. Or the Love Unlimited Orchestra.
Everyone is totally overthinking it here. Obviously, he was hoping someone would follow up with “Wait for it! – dary!” (or in his case “Derry”, 'cos of him being Irish).
I always thought Irish people were using “gorgeous!” in a very different manner than I would. Then I learned that they might actually be saying “comhghairdeas!” (“congratulations!”).
In addition to the “Right!” = roughly “alright, everyone, listen up”, of British English, the Brits also throw the word “right” around as an adjective modifier. “This place is a right shithole.” “You’re a right wanker.” They also say “right through.” When Elvis Costello and the Attractions covered I Can’t Stand Up For Falling Down, originally by Sam and Dave, they changed “I’ve wrestled with tears” to “I’m right through with tears,” in appropriately British fashion.
Yes, synonymous with “real” as an intensifier.
But this usage is not colloquial in any British dialect that I’m aware of. I would take it as poetic.
Ditto. I’ve never in my life heard of a frown being anything other than a downturned mouth. I mean, I guess a person could furrow their brow when frowning, but it’s not any more part of a frown than squinting their eyes or throwing up their hands at the same time would be.
I am in New Jersey and I use “wicked” that way - but that’s BECAUSE it’s not commonly used here, even though we’re in the northeast and practically adjacent to New England. To my ear, it sounds a bit exotic, and it just sounds wicked cool.
Assez can be used in France in much the same way often enough. Though it might be more common to hear an exasperated mother hissing “Ça suffit!”
May be wandering off at a tangent, but cognate words in different languages can often be “false friends”, especially when it comes to idiomatic use, and particularly swearwords. “Con” in French means little more than “idiot” (potentially an irritating or tedious one, perhaps), but the English cognate is about the most forceful insult there is (though in the UK, the word “twat” - which was once commonly used in the same physiological sense - probably has about the same level of insulting force as “con”). Which is why it can be so difficult to translate swearwords: do it literally, and you end up with parody Hemingway (“I spit on your grandmother’s unmentionable!”, and so on).