How to Not swear on the Moon
From this article by spaceflight historian Amy Shira Teitel:
One [astronaut] in particular had the unfortunate habit of filling space when his mind wandered with profanities. This posed a problem for NASA — with the world watching astronauts walking around the lunar surface, how could the organization be sure the his transmissions from the Moon would be family-friendly?
The story goes that in preparing for his mission, NASA had the astronaut hypnotized. Rather than curse, a psychiatrist put the idea in his head that he would rather hum when his mind wandered. The hypnotized astronaut is rarely named, but only one man can be heard humming as he skipps across the lunar surface. Transmissions from Commander Pete Conrad are punctuated with “dum de dum dum dum” and “dum do do do, do do” making him the likliest candidate.