>>15240
A postcard from 1905; the Flatiron Building in the background shows that 23rd Street is the location. This is the most widely known explanation for the phrase "23 skidoo".
23 skidoo (sometimes 23 skiddoo) is an American slang phrase popularized during the early 20th century. It generally refers to leaving quickly, being forced to leave quickly by someone else, or taking advantage of a propitious opportunity to leave, that is, "getting [out] while the getting's good." The exact origin of the phrase is uncertain.

23 skidoo has been described as "perhaps the first truly national fad expression and one of the most popular fad expressions to appear in the U.S," to the extent that "Pennants and arm-bands at shore resorts, parks, and county fairs bore either [23] or the word 'Skiddoo'."[1]

"23 skidoo," first attested in 1906, combines two earlier expressions, "twenty-three" (1899)[2] and "skidoo" (1901), both of which, independently and separately, referred to leaving, being kicked out, or the end of something. "23 skidoo" quickly became a popular catch-phrase after its first appearance in early 1906.[3]