When did people stop calling it a Mobile?

> the office phone would have been gross, and of course anyone could use it. Probably could give you a disease.  Just ask the Golgafrinchams, oh you can't because they're all dead. Golgafrincham was a planet, once home to the Great Circling Poets of Arium. The descendants of these poets made up tales of impending doom about the planet. The tales varied; some said it was going to crash into the sun, or the moon was going to crash into the planet. Others said the planet was to be invaded by twelve-foot piranha bees and still others said it was in danger of being eaten by an enormous mutant star-goat. These tales of impending doom allowed the Golgafrinchans to rid themselves of an entire useless third of their population. The story was that they would build three Ark ships. Into the A ship would go all the leaders, scientists and other high achievers. The C ship would contain all the people who made things and did things, and the B Ark would hold everyone else, such as hairdressers and telephone sanitisers. They sent the B ship off first, but of course, the other two-thirds of the population stayed on the planet and lived full, rich and happy lives until they were all wiped out by a virulent disease contracted from a dirty telephone.