Of Irish origin, coming from the Kerry/Cork region, predominantly used in order to signify one's complete lack of interest in any given topic.
Akin to what one may describe as a "fuck it" attitude.
Can also be used as a precursor to an aggressive reply when asked a question
-"Whats the score in the Ireland game John?"
-"was yer wan any good in the sack?"
-"yerra, would you ever go away and fuck yourself"