Why did we choose tant pis?
It's a expression that you'll hear frequently used in everyday conversation. On top of that, it's one that's almost impossible to guess the meaning of and sometimes it's not even clear which context to use it in because you'll hear it said in such a variety of tones. And you need to know how to pronounce it.
So, what does it mean?
Literally speaking, tant pis means 'so much the worse'.
The reason why it can be said in different tones depending on the situation is that it can mean something fairly mild like 'oh well' but it can also mean 'tough' or 'tough luck'.
A synonym in French could be c'est dommage, or quel dommage (what a shame) and if something disappointing or sad has happened a more appropriate synonym would be c'est dur (that's hard).
Il n'y a plus de lait. Tant pis, je boirai mon café noir! – There is no more milk. Oh well! I'll drink my coffee black.
Si ça ne t'intéresse pas, tant pis pour toi, je le proposerai à quelqu'un d'autre. – If it doesn't interest you, too bad for you, I'll suggest it to someone else.
(The above two examples are from wordreference.com)
C'est tant pis pour lui. – That's just too damn bad for him.