"Nothing to tell" versus "nothing to say"

There's nothing to tell.
There's nothing to say.

Can anyone explain the difference between those two statements and give some examples on how they should be used? I think I do have a basic understanding, but I'd like to hear it from someone who knows this to the deepest roots.

Solution 1:

"There's nothing to tell" is a response to someone's asking for details about an event or a story, where the responder implies that the information the asker wants to know doesn't actually apply to the event or story. For example:

Q: "What happened at the party last night?"

R: "There's nothing to tell."

(Nothing happened or things that you don't really care about happened, but that's it - i.e. I hung out for five minutes and went home.)

The responder could also say, "There's nothing to tell," in order to downplay what actually happened. For example:

Q: "It must've been really hard to become such a good swimmer. How did you do it?"

R: "There's nothing to tell."

(The answer is too long and/or boring, so I'll spare you the details.)

Another instance is your own suggestion of using "There's nothing to tell" to mean, "I don't want to tell you what happened."

"There's nothing to say" is very similar to "There's nothing to tell" in that the responder thinks any response the asker might expect either doesn't apply or doesn't matter. It's also possible that the responder doesn't really want to answer the question. The biggest difference is that "tell" generally involves some sort of story or narrative, and "say" involves some sort of issue or non-narrative topic. For example:

"I would love to visit Area 51. Wouldn't you?"

"There's nothing to say."

(I don't think it exists, so my response doesn't apply.)

"Do you think signing that bill into law was the right decision?"

"There's nothing to say."

(It doesn't matter what I think.)

Solution 2:

The ‘Cambridge Grammar of English’ by Carter and McCarthy (not to be confused with ‘The Cambridge Grammar of the English Language’) shows that the two words differ on a number of points of syntax. For example, say cannot be followed by an indirect object, but tell can be (I told her, but not *I said her). I can give details of other differences if you want them.

As far as meaning goes, tell focuses on the content or message of what is said, while say focuses more on the words someone says. So, There's nothing to tell suggests there’s no story, no incident has occurred, nothing to satisfy anyone’s curiosity. There's nothing to say means that something may have happened in which others might be interested, but there’s no point in saying what it is. A couple of examples might help.

TELL

A. Hey, what happened to you last night? I wanna hear all about it.

B. Nah, nothing. Really, there’s nothing to tell.

SAY

A. Are you just going to leave me? No explanation? Just walking out like that?

B. We’ve been through it all before, haven’t we? There’s nothing to say.