Origin of expression

Does anyone knows where I can find out about the origin of the expression "gone tits up". Is it a euph. for death? When did it start?

[Tdol]

It means things have gone wrong- if you fall over on your back, your tits (if you're a woman) are up.

[curmudgeon]

Its a ruder version of 'gone belly up' meaning things have gone drastically wrong. A fish goes belly up when it dies, so maybe thats where it originated

[Naughty Beef]

Yeah curmudgeon, that's what I was going to say.
'gone belly up' is easily explained, and it naturally leads to 'tits up' . Just like how 'I can't be bothered' evolved to 'I can't be arsed'- via 'I can't be bovvered'.