Union contract (6)
(Other definitions for ido that I've seen before include "a language? That's unnatural" , "Say yes in marriage" , "Prepared tongue" , "Required affirmative in wedding ceremony" , "Wedding promise" .)
(Other definitions for prenup that I've seen before include "Legal agreement before marriage" , "Financial agreement in case of divorce made by a couple before marriage (abbr)" , "Agreement drawn up before the wedding" , "Contract between those about to marry" , "arrangement before marriage" .)