As Julia Cresswell writes in “The Cat’s Pyjamas,” most terms containing “blow” have to do with losing one’s temper or becoming so angry that one loses all self-control. But the exact origin of the term is unknown -- as is its intended visual. Cresswell writes that the phrase “blow one’s top” is believed to draw on the image of oil wells under pressure because, if not properly monitored, these structures could erupt and send streams of black liquid into the air. But the phrase might also relate to pressure caused by steam or water power.