Q. How would you pluralize “ram’s horn” when there are seven of them (i.e., more horns than one ram would naturally have)? Logically, it should be “rams’ horns,” but there is an argument that this should be treated in the same way as cowhides or sheepskins. In that case, wouldn’t it be “ram horns”? There are also votes in the office for “ram’s horns.”
A. Since cowhides and sheepskins are closed compounds, they aren’t relevant (and in any case you can’t combine rams and horns without getting “shorn”). Since “seven rams’ horns” suggests fourteen horns, “seven ram’s horns” seems clearest.