An OED library researcher has uncovered evidence from April 1978, following a lead from Dr John Bailiff
We are looking for earlier evidence of Ironman in the sense ‘a triathlon consisting of a 2.4-mile swim followed by a 112-mile cycle race and a full marathon’. The first example found so far is from 1979, but the first race of this type is said to have been held in Hawaii in 1978.
1979 Sports Illustrated 14 May 90/2 The Iron Man contest was born when someone wondered what would happen if endurance tests in swimming, bicycling and running were piled on one another in a single event.
Can you find earlier evidence? Local Hawaiian publications, specialist magazines, or promotional materials from the competition itself would be good places to look.
Posted by OED_Editor on 8 October 2012 6.26