Original Ice Dragon?

In the video "trailer" for his new children's book, The Ice Dragon, George R. R. Martin posits that he is, as far as he knows, the first fantasy author to imagine a dragon that breathes out cold instead of fire.

Ruth Plumly Thompson created such a creature in Ojo in Oz (1933). Colored blue and puffing out frost, it runs endlessly around Crystal City, keeping the inhabitants frozen solid. Ojo is one of Thompson's better contributions to the Oz series, but there's no reason for Martin to know of it. And I don't know if Thompson was first with the ice dragon idea, either.

The detail of Martin's interview that caught my attention is that he originally wrote his tale over twenty years ago, as a short story for an anthology. What has changed? His name has become much more famous, and the market for children's fantasy has exploded. Now a short story can be republished, with big type and lots of illustrations, as a 100-page novella.