An Australian expression wishing misfortune on the recipient, similar to "eat shit and die". "Jocks" is a general Australian term for underwear, so you are more or less wishing the person an acute attack of explosive diarrhoea.

As heard in the popular Aussie film "The Castle".
Daryl Kerrigan to opposing counsel, after winning court case: "Suffer in your jocks!"
by Choda Boy 57 August 24, 2006
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