Symbolism, Imagery, Allegory
Mont. That is,
Plenty of horns hath made him poor of horns.
Cam. What should this mean?
Mont. I 'll tell you; 'tis given out
You are a cuckold.
Cam. Is it given out so?
I had rather such reports as that, my lord,
Should keep within doors. (2.1)
Monticelso is telling Camillo that it's widely known his wife has cheated on him. But he's using this folk tradition—common everywhere from England to Vietnam—comparing men who've been cuckolded to stags. It's said that a cuckold—like a stag—has "horns" (or, technically, antlers).
Why stags, you ask? Well, stags steal each other's mates. If a stronger stag beats a weaker stag in a fight, he can steal that stag's doe. Hence, the use of the term "horns."
(The word "cuckold" is itself actually a reference to another animal, the cuckoo, since it incubates its eggs in the nests of other birds—the same way a man could end up raising children that he thinks are his own but really aren't.)