Glad I read the Additional Details. Yes, "lunch box" is a slang term for a man's genitals. Of course with slang, never assume that everyone will understand it (or appreciate it). People get so creative talking about things like this. A couple of rather British expressions for the same thing are "the crown jewels" and "meat and two veg" (which might explain the "lunch box" phrase).

reference to Peachey: it would be very interesting to have a relation of metaphores applied to genitals, both masc and fem, in all languages of the world. Pity, that most peole apply "taboo" label not only to the use of them but also to the description of such ocurrences.