Q: How did an “intercontinental ballistic missile” become an “ICBM” instead of simply an “IBM”?
A: The original abbreviation for “intercontinental ballistic missile” was indeed “I.B.M.” (with dots), and some standard dictionaries—Merriam-Webster Unabridged, for example—still include both “IBM” and “ICBM” as the abbreviations.
The earliest example we’ve found for either initialism (an abbreviation that’s spoken as letters) is from the July 27, 1954, issue of the Birmingham (AL) News:
“In the year 1960, by the agreed estimate of the Pentagon’s official analysis, the Soviet Union will fly its first intercontinental ballistic missile. That missile, or I.B.M. as the experts call it, will be an accurately guided rocket, comparable to a giant V-2, capable of carrying a hydrogen warhead over a range of 4000 to 5000 miles.”
The earliest example for ICBM that we’ve seen (from the May 30, 1955, issue of Newsweek) explains why the longer term is more common today:
“The Air Force is now calling the Intercontinental Ballistic Missile the ICBM instead of the IBM. Too many people got the missile confused with International Business Machines Corp.”
We found both examples above in “Among the New Words,” a column by I. Willis Russell, in the May 1957 issue of American Speech.
Finally, here’s an early “ICBM” example cited by Russell that seems relevant now:
“The ICBM—the intercontinental ballistic weapon—has become, even before its first test flight, part of the language of power politics” (from the June 2, 1956, issue of the New York Times Magazine).