RAS syndrome and U.S. trademark law
by tepples (727027)

The joke is often repeated. But U.S. trademark law may help explain RAS syndrome. Trademarks are adjectives and should be used with a generic term, even if they contain an abbreviation of the generic term. Hence "TCBY yogurt" even though "TCBY" is "the country's best yogurt", "DC comics" even though "DC" was "detective comics", "SAT reasoning test" even though "SAT" was "scholastic aptitude test", and "SPAM luncheon meat" even though "SPAM" stood for "specially processed assorted meat" at one time. Writers pressured by trademark owners to include the generic terms in their copy tend to overextend the habit of abbreviation + generic even to cases where the abbreviation is not a trademark.

Another cause is to disambiguate homophonic or homographic acronyms. "Put your PIN in the computer" could be misheard as "put your pin (or pen) in the computer", which could damage the machine. "Put your PIN number in the computer" has one interpretation.