slaan = (verb) to hit, strike

If you think somebody makes a really stupid or unfriendly remark you think isn’t fair, you can use either one of these expressions:

Waar slaat dat op?

What’s  that got to do with it?
(Or: What did I do to deserve this?)

Dat slaat nergens op.

Come on, it’s got nothing to do with it
(Or: That’s unfair)

(stronger, more irritated:)

Waar slaat dat nou weer op?

What on earth has that got to do with it anyway?
(Or: you are talking nonsense)

(Used in a subclause, less irritated:)

Ik snap niet waar dat op slaat.

I don’t understand what that’s got to do with it.
(Or: I lost it completely)

And last but not least:

Dat slaat als een tang op een varken!

(lit: That hits as a pincer on a swine)
It makes no sense at all.