This claim is surprising. The Psychomech trilogy (published in the mid 1980s) involves deliberate cryonic preservation of multiple characters in the hope that when one of them becomes a functional god he'll be able to resurrect them. In that case, one of the characters who is preserved is the love-interest of the protagonist. And the later books in that series imagine a world in a not too distant future where cryonics is extremely common. Lem's "Fiasco" deals with medical cryonics and is also from the 1980s. Pohl's "The Age of Pussyfoot" also has explicit medical cryonics, albeit with a somewhat reactionary message.

Ettinger himself was inspired to think about cryonics as a practical thing from the short story "The Jameson Satellite" (admittedly fairly obscure).

As a matter of pure anecdote, I had encountered the idea in multiple contexts when I was about Harry's age, and Harry if anything has been exposed to more scifi than I had at that age.