The idiom knock one’s socks off originated in the mid-1800s, though with a different meaning than it carries today. We will examine the meaning of the expression knock one’s socks off, where it came from and some examples of its use in sentences.
To knock one’s socks off means to impress someone favorably or to surprise someone in a positive manner. This meaning of the term knock one’s socks off seems to have come into use in the mid-1900s, though the idiom knock one’s socks off was coined sometime in the mid-1800s. At that time, knock one’s socks off meant to soundly beat someone, either physically or figuratively. This secondary meaning is still occasionally used. The idea behind the expression knock one’s sock’s off is to deal someone such a blow that not only is he knocked out of his shoes, but he is also knocked out of his socks.
If you want to get the father figure in your life something super cool to knock his socks off, you have to get creative. (The Huffington Post)
“If it’s a knock-your-socks-off performance by him, I think they try to get that locked down quickly.” (The Columbus Dispatch)
He hasn’t produced like a guy who is going to come in and knock the socks off of a franchise offensively yet though, but there’s at least a reason for that. (The Dallas Morning News)
Her performance at the Auditorium Theatre was anticipated by Tribune critic Sid Smith as “likely to knock our socks off.” (The Chicago Tribune)