When Hurley was complaining to Locke about his food pantry job, Locke called him "Hugo". Something along the lines of "We've all got a job to do, Hugo."

I thought nobody on the island knew his real name. Certainly not Sawyer when he was reading the messages in the bottle.

He called him Hugo in Exodus part 2 aswell, I think.

Maybe he read the manifest.

I thought it was odd that Locke kept saying Hugo at the end of every sentence. Maybe he saw the plane manifest at one time?

Hurley told Jack his name was HUGO when he mentions doing the Census... he says something like... we don't even know who everyone is, my name isn't even Hurley, it's Hugo. So, either Jack or Hurley has also told (off camera) other people that his name is Hugo. And, it would be Hugo on the manifest as well.

Hurley told Jack his name in "Raised by Another." It's entirely possible he told other people his name off screen or Jack told other people. Look at the pilot episode. The only people that see the pilot die are Charlie, Jack, and Kate. But when they shoot the polar bear Boone says "is that the same thign that killed the pilot?" Obviously one of the three had told him about it OFFSCREEN.

It's not so hard to believe that stuff goes on on the island that we don't see.

Which brings up another point, maybe I missed.

Locke tells Jack in Orientation: "Desmond had a gun to my head, and you came in." or something like that...

When did Desmond tell Locke his name?

He tells him his name before Jack shows up:

DESMOND: So the world is still out there?
LOCKE: As far as I know. Could you tell me your name?
DESMOND: My name? My name is Desmond.

Thanks sledgeweb. I missed that...

Yeah, Locke has called Hurley, Hugo several times. Not sure about the exact episodes. Also, if Hurley did tell people his real name, it couldn't have gotten around to many other people because like ericfish said, Sawyer didn't know his name was Hugo, and apparently neither did Michael, because he didn't say anything when Sawyer said "Who's Hugo?".

It seemed to be emphasised that he was saying "Hugo" as if on purpose to get a reaction from Hurley. Why else continually state his name at the end of almost every sentence. Hugo, I mean Hurley, I mean Hugo,...no Hurley didn't seem to catch on, know what I mean yeah?

YES.

Locke was laying it on really thick. He ended EVERY sentence with "Hugo."

It was BIZARRE.

How about the fact that Hugo owns a box company and Locke worked at a box company? Could be the same company.

Its possible that off camera jack has called Hurley 'Hugo' and others overheard and its caught on. Yeah, it was odd that Locke used his name so much in the same conversation, but, well, stranger things have happened on the island havent they? haha
Besides that, there are 30 other people on the island, we dont know whose names Locke knows, or Jack knows, etc, etc, but i am certain that they would know the names of most of, if not all of, their other, forgotten Lostaways. If they were to call another of the forgotten lostaways by their name it wouldnt raise an eyebrow...

How about the fact that Hugo owns a box company and Locke worked at a box company? Could be the same company.

I was just going to say that because according to the exclusive Hugo "Hurley" Reyes "trading card" that came in the September 16th issue of Entertainment Weekly, Hurley bought a box company that Locke works for with his lottery winnings.
That was never revealed in the Numbers episode, but I guess it's possible to make that connection.