When the idea of Desdemona having an affair first starts to become implanted in Othello’s head, Shakespeare uses alliteration to emphasize his franticness. Raving that his “tranquil mind” is already lost and demanding Iago give him further proof, Othello says:
If thou dost slander her and torture me,
Never pray more. Abandon all remorse;
On horror’s head horrors accumulate
Here, the use of alliteration in the final sentence, through the repetition of the "h" and the "r," creates a verbal picture of the accumulation being described. Just as the horrors described breed more horrors, so do the sounds and letters in the sentence pile on top of each other. The alliteration draws the audience’s attention to the meaning of the sentence and emphasizes its importance, with the idea of the self-sustaining nature of vices proving central to the play. Jealousy, the vice which will bring around the play’s ultimate tragedy, is described by Emilia in the play as the monster “begot upon itself, born on itself”. And indeed it will only take one small seed of jealousy to be sewn in Othello for it to multiply itself and lead to the escalation of violence in which the play ends.
Shakespeare uses alliteration to emphasize the extent of Othello’s despair after he realizes he has been tricked and is forced to come to terms with the gravity of his mistake in killing Desdemona. Looking to the bed where his dead wife lies, Othello describes how he deserves to be punished in hell before crying:
“O Desdemon! Dead, Desdemon! Dead! O, O!”
Here Shakespeare uses alliteration both in the repetition of the "d" and "o" sounds to reflect Othello’s woe. The repetition of the "d" in "dead" and "Desdemon" is an example of consonance (the repetition of consonant sounds). This emphasis on the dental "d" sound coupled with the repetition of the monosyllabic "dead" and "O" gives the sentence a short, staccato rhythm, creating a harsh sound which mirrors the discord of the scene. The shortness of the sounds also gives a sense of finality and decisiveness, which reflects the finality of Othello’s actions and his realization that there is no undoing what he has done.
The choice to repeat the "d" also draws attention to Desdemona’s name, which means ill-starred or wretched, a choice which presents Desdemona’s miserable ending as inevitable. That Othello refers to Desdemona as an "ill-starred wench" just lines before suggests that this link is intentional.
Furthermore, the use of assonance (the repetition of vowel sounds) in the repetition of "O" aurally represents Othello’s despair. The babbling repetition gives Othello’s speech a sense of frenzy which highlights his struggle to comprehend and articulate his actions, as well as his growing madness throughout the play. Shakespeare’s attention to techniques such as alliteration is particularly important in the context of a play, where the sounds of words spoken aloud are especially effective in portraying emotion to the audience.
The verbal excesses of Othello’s speech also emphasize his differences with Iago, who chooses silence when his crimes are exposed. By contrast with Iago’s coldness, Othello’s impassioned speeches, aided by Shakespeare’s use of devices such as alliteration, emphasize his humanity.
Before Othello kills himself, Shakespeare uses alliteration to emphasize the link between love and violence which is central to the play. Speaking to the already dead Desdemona, Othello says:
I kissed thee ere I killed thee. No way but this,
Killing myself to die upon a kiss. [he dies]
Here, the alliteration of the "k" in "kissed" and "killed" draws a clear link between these words, which are only separated by one difference in letter. The verbal similarity of these words echoes the sentiment of Othello’s speech: that there is but a thin line between passion and violence. The link between love and violence is repeatedly emphasized in Othello and Desdemona’s relationship. Desdemona, after all, fell in love with Othello after hearing stories of his “suffered” past—“she loved me for the dangers I had passed, and I loved her that she did pity them,” Othello says in the first act. The choice to come back to this theme at this climactic point reiterates its centrality, not only in their relationship but indeed the whole play.
The verbal symmetry of Othello’s phrasing—in the pattern of kissed, killed, killing, kiss—also reflects Othello’s attempt to restore balance and order in this scene. The verbal pattern of kissed, killed, killing, kiss structurally reflects the stages of Othello and Desdemona’s relationship, which starts in love, progresses to violence, and then ends in final declarations of love again. Othello’s linking of killing and kissing couches his violence in romance. By claiming he is "killing himself to die upon a kiss," Othello tries to convince himself and the audience that his acts of violence were done with love in mind: the greatness of his love is proportional to the horrors of his violence. Whether this is successful or not is up for debate, but the attempt to forge the link through language is clear. The verbal symmetry suggests a need to forge balance, with Othello’s final act of self-sacrifice an attempt to enact justice for his own crimes.