S is a non-mileage earning class.

The economy class codes that earn on Etihad, as you will see from their website, are:

Economy Class E, U, V, L, Q, G - 50%
Economy Class M, K - 75%
Economy Class H, B, Y - 100%

Anything else won't earn you any miles.

It's highly unlikely that any of their partners would credit miles for classes that Etihad themselves don't credit for.

The Korean website shows that the following Etihad economy class codes do not earn anything: E,I,N,O,U,S,T,V,X,Z (note that, until 27.10.2013, X was a 150% earning business class fare, and E was a 100% earning economy class fare)