Here's a breakdown:
* Mad dogs: This refers to dogs acting erratically and potentially aggressively due to the heat. It's a metaphor for people losing their cool in the summer.
* Englishmen: This refers to the stereotype of English people being stiff upper-lipped and persevering even in uncomfortable situations. Coward is suggesting that even the famously stoic Englishmen are affected by the heat.
The line is ironic because it implies that both mad dogs and Englishmen are unpredictable and potentially dangerous in the summer heat. Coward's song is full of witty observations about the absurdity of human behavior in such conditions.
The line has become a popular phrase used to refer to:
* The unpredictable nature of people in extreme heat
* The contrast between perceived stoicism and actual human behavior
* The absurdity of taking oneself too seriously, especially in uncomfortable situations.
So, the next time you find yourself sweating in the summer sun, remember "Beware of mad dogs and Englishmen" and try to keep your cool!