Within Act 3, Scene 3, we see how Iago is plaguing Othello constantly with crude sexual imagery of Desdemona. Here, he says that 'Would you, the supervisor, grossly gape on? Behold her topp'd?'
Iago presents the idea that the utmost proof is to see Desdemona have sex with another man. Othello would rather be dead than witness that. Yet, such crude language increases Othello's sexual jealousy as well as tarnish his view of Desdemona