Language / What's the meaning of 'na nie' in Piosenka na nie of Makowiecki Band [3]

Oi, lads and gals from the world over.
Long and short is I adore Makowiecki Band. And one of my my fav pieces they sing is called 'Piosenka na nie'. But what's the meaning of 'na nie'? I did a google search, but to no avail. Just my luck lol

Btw I also heard 'na tak', for instance 'jestem na tak'. What on earth should that mean?)
Many thanks in advance, and recommend Makowiecki band to everyone who mightn't have listened to them yet.