Symbolism, Imagery, Allegory
All Choked Up
Most people have a pretty positive association with blowing out candles: it's what we do on our birthdays before chowing down on some delicious cake.
Well, sorry to put a damper on your b-day traditions, but in Othello blowing out candles is synonymous with strangling your wife to death.
The candle that Othello blows out just before he puts a choke-hold on Desdemona symbolizes Desdemona's fragile life. Othello draws the comparison himself—as he stands over a sleeping Desdemona with a lit candle in his hand, he says he's going to "Put out the light, and then put out the light" (5.2.7): he's going to blow out the candle (the first light) and then strangle Desdemona (the second light).
He also muses that the difference between Desdemona's life and a candle's light is that he can put out and relight the candle over and over if he so chooses, but he can kill Desdemona only once:
"If I quench thee, thou flaming minister, / I can again thy former light restore, / should I repent me," he says to the candle. "But," he says to the sleeping Desdemona, "once put out thy light, / Thou cunning'st pattern of excelling nature, / I know not where is that Promethean heat / That can thy light relume" (5.2.8-13).
Yep, that's pretty creepy.