You can adopt an air of nonchalance, a fake British accent, or even a stray dog. When you adopt something, you consciously select it and accept it as your own.
“Adopt, adapt, and improve,” says the thief in a Monty Python skit when he robs a lingerie shop instead of a bank. Adopt is to take something over, and to adapt is to change something to suit your needs. It’s helpful advice when you ask for money and get a pair of granny panties.
The robber didn’t invent the motto, it’s from the Round Table Club, and it comes from a speech made by the Prince of Wales in 1927.