In the essay “Wit and Witchcraft: an Approach to Othello” Robert B.
Jealousy in Othello is what the play was founded on.
Othello: A noble "Moor", in the service of the Venetian State, Othello is introduced to us in the very first scene by the term "Moor", when Iago complains that Othello has made Cassio his lieutenant and not him. We also learn from Iago that Othello has a relationship with the fair Desdemona. Respected by the Duke of Venice, who is the first to address him by name (Othello in Act I, Scene III) and who sends for him when Cypress is threatened by Turkish forces, Othello is continuously described by his critics (Brabantio, Iago) as a "Moor" a reference to his dark skinned appearance and a reference to the race of Muslim peoples of north-western Africa to which Othello belongs.
What others think of you is not necessarily always truthful.
Though made Governor of Cypress in Act I, Scene III, Othello's fortunes rapidly change for the worst as Iago succeeds in making Othello believe his loyal wife is having an affair with his lieutenant Cassio, a belief that leads to Othello killing his loyal, loving wife and later himself when he realizes that he was wrong and merely tricked by Iago.