When/how did 'up' come to mean 'wrong'?

In the phrase ‘what’s up’ and ‘something’s up’, ‘up’ clearly means wrong, amiss, different in a negative way.

How did a word meaning the opposite of down become another meaning for ‘wrong’.

And why ‘up’ rather than ‘down’ which would seem to make morse sense?

Hm, maybe its because they sound the same and run together (by that I mean the uh). Whats (wuhts) up, and somethings (suhmthings) up. That’s my guess.

It doesn’t mean wrong, it mean’s something’s astir, something’s happening. American’s use it as a greeting “What’s up?” “Nothing, how 'bout you?” “Not much”. The answer is not presumed negative.

I don’t know morse code, so maybe it does make sense in that form of communication.
But ShibbOleth is right; What’s up just means ‘whats’s the haps, man?’, and ‘something’s up’ just means something is goin’ on.

As to down making more sense, I guess you could say:
"What’s down, dude? And then the answer would be either,“I am”, or “Not me man, I’m just peachy keen”.
Are you down with that?

“What’s going down?” seems a lot more “negative” to me than “yo, what’s up?” does.

The tone is everything here. If I say in a sympathetic voice “hey, what’s up?” I’m probably asking what’s wrong. If I say “What’s up?” in normal conversation, or when I see you, I’m probably just asking what’s going on.

Think of the statements as
“What is up and moving around?”
“Something is up and moving around.”

I would also agree that “What’s up?” has no implicit or explicit negative connotation outside of context. “Something’s up.” may more frequently be used in a negative manner, but it still relies on context.

To add some context via the OED, they offer as first cites(subject to more modern electronic database searches)

It certainly does not mean that. How you find it “clear” is beyond me. Replace the word “up” with the phrase “going on” and you have an accurate rendition of the meaning. In some situations there might be a sense of something amiss, but that is most definitely not the case in all situations where those phrases might be used.

For all those who accept that ‘what’s up?’ doesn’t have a negative connotation I have a question.

Considering that where I come from, ‘what’s up’ does indeed mean ‘what’s wrong’, and that phrases adopted for one meaning often come from a valid, older meaning (i.e. the phrase ‘what’s up’ as a greeting may have originated from the same phrase as an inquiry of the nature of distress)

why does the older meaning use ‘up’ as ‘wrong’?

The word “up” has many different uses.
dictionary.com

I owe you an apology. I assumed you were in the U.S. and my response applies to the way I’ve heard those phrases used here in the States. Now that I see where you are, I defer to your understanding of their meaning in your locale. I’m sorry for my unhelpful repy.

As to whether either meaning might have come from the other, I don’t know.

Hey Gary, No need to apologize. My post was designed simply to supply information which I had neglected to provide in the OP. I shouldn’t have expected people to automatically know what meaning of ‘what’s up’ I was refering to.

To be fair to the OP, I just read about 5 early uses of the expression in US newspapers from the 1850’s, and it almost always meant “what’s the matter?”

We’ve all been corrupted by Mel Blanc, Chuck Jones, and Tex Avery.

You’re out walking when you notice your companion has frozen in his tracks, curiously looking around sniffing the air.
“What’s upwind?” you ask.

FTR, I am upset that I never just invited myself up to Akron to see Samclem’s library back when it wasn’t so far away. It must be a marvelous place.