What is this article of clothing called?
A dickey is a type of false shirt-front, originally known as a detachable bosom - designed to be worn with a tuxedo or men's white tie, usually attached to the collar and then tucked into the waistcoat or cummerbund.
Better dickeys have a trouser tab at the end to secure them down, preventing the dickey from popping out. The rigid plastic dickey came into fashion in the latter years of the 19th century, and was one of the first successful commercial applications of celluloid.
The invention of the dickey was to make the bosom front of a full dress shirt a separate entity in itself, like the detachable collar, so it could be laundered and starched more easily than a traditional shirt with the bosom attached.
The etymology can be attributed to Cockney rhyming slang where a "dicky dirt" is a shirt. Additionally, British office workers were required to wear suits, but their wages made it difficult to keep a fresh supply of laundered shirts.
Recently, dickeys have been rising in popularity. In 2011, dickeys and menswear inspired lingerie became popular as a break from minimalist and restrictive fashion at the time.
At the same time, detachable collars and dickeys were showing up on the runway as peter pan collars. In 2013, the materials used for dickies was expanding from knits and cotton, to leather and silk.