I've heard the word cochar, in Venezuela, which is a vulgar way to name sex. Coshar, does not exist in Spanish.
coshar is incorrectly written, and should be written as "kosher" being its meaning: It is the approximate way that sounds like the Yiddish word for the Spanish " kosher " that comes from the Hebrew 1499; 1464; 1468; 1513; 1461; 1473; 1512; ( kosher; that properly respects the Jewish precepts for food that can be consumed by practitioners ).
It is not recognized in the Royal Academy of the Spanish language. Apparently, certain Latin American countries uses that Word colloquial or commonly to say that going to bed with someone or have sex.