Yes, it's from Heinlein's novel. When I first started looking for it (around 1969) there was no Internet! It wasn't in any printed dictionary. My father (an engineer) had never heard the word, neither had anyone else. I haven't been looking for it every day of the last fifty years, but it has been bugging me that Clarke used a word that I didn't know and have never seen used anywhere else. Anthony Burgess works are full of words I don't know, Sci-Fi not so much. I have read some of Heinlein's stuff but not that particular work, which I was unaware of before today.