Census from responses:
Eat hats: English, French, Norwegian, Swedish, Danish*, Icelandic, Hungarian, Finnish, Estonian*, Hebrew
Do not eat hats: German, Russian, Spanish, Italian, Polish, Yiddish, Mandarin Chinese
Contradictory data re: hat-eating: Dutch
* Hat may optionally be "old"
Provisional unified theory of hat-eating (highlighted countries eat hats to express an unlikely event has occured)
The major outstanding question here is whether they eat hats in Estonia*. Is this a universal feature of Uralic languages
* Update: YES
@mcc — Estonians do eat hats, but on a different occasion. Specifically when they believe that something’s impossible e.g., “I’ll eat my [old] hat if Estonians land on the dark side of the moon.” We’re one confident nation 😅
https://sõnaveeb.ee/search/unif/dlall/dsall/oma%20mütsi%20ära%20sööma/1
@boxyrobot ah, that's the same as the English expression— my "shame and anguish" comment was just me being cutesy.
The "old" is a bit of a surprise, not sure I've seen that in other variants of the espression