In European medieval and renaissance love poetry, the handkerchief is typically a symbol for a woman's romantic favor. For instance, there was a particular ritual in which a lady would drop her handkerchief for a knight to pick up and keep as a token of her regard. The handkerchief that Othello gives Desdemona is, similarly, a love-token and therefore a symbol of their love. But the handkerchief, which originally belonged to an Egyptian sorcerer, also comes to symbolize the illusions that Iago is "casting" through his plotting and subterfuge.
Othello is rife with animal metaphors. In particular, this language is used to describe Othello, the "Barbary horse," or the "beautiful creature" Desdemona. In each case, the animal language is connected to prejudice. Describing a person or group in animal terms is a way of defining that person or group as being less than human, something that deserves to be humiliated and controlled.