"I wanta make the King of England keep his blasted snoot out of America."
- William Hale Thompson, candidate for Mayor of Chicago; Time Magazine, National Affairs: Mud-Slinger v. Rats February 21, 1927.
Snoot is a Scots word for snout or nose which has been adopted into American English as an informal and slangish way of referring to the nose or face. Its usage peaked during the first part of the 20th century, mostly in variants of the phrase "punch him in the snoot". A less common idiom, 'to cock a snoot' (originally 'cock a snook'), means to thumb one's nose'.
"Mr. Coolidge Lams Mr. Thompson the Snoot."
- The Capital Times (Madison, Wisconsin), April 1, 1928·
This is the most likely root of the word snooty. Back in the early 1900s snoot was used to refer to rude expressions of disdain and wrinkling one's nose (a small child's snoot might also involve sticking out one's tongue). This became specific to the act of turning up one's nose, and then to a disdainful and snobbish attitude in general.
"In due time Constable received a rumpled postal card, which informed him that Kani Natupski 'Snoots at American law.'"
- Our Natupski Neighbors by Edith Miniter, 1916.
And finally, snoot returned to being a noun once again, this time refering to a snooty person. These sense of snoot are still around, but Google indicates that all of these senses of snoot put together are perhaps as frequently used as the technical usages of the term -- snoot also refers to an attachment for a spotlight or camera to guide light.
"A snoot can be defined as somebody who knows what dysphemism means and doesn't mind letting you know."
- Critical Encounters with Texts by Margaret Himley and Anne Fitzsimmons, - 2005.
Brevity Quest 2016