Expressions used in Everyday Spoken English in Social and Professional contexts
To rattle somebody can mean to behave towards someone in order to make them lose their composure or gain a psychological edge over them. That's why in social situations the word is commonly used in connection with sport. In a professional setting, you may want to rattle somebody if you are in competition with them, or if you want to test their character. A related expression is to 'rattle someone's cage.' To 'rattle' means to shake something in order to make noise. As a noun, a 'rattle' refers to a toy often given to babies.