Meaning of あまりのことに

Question

Maruko's sister doesn't seem to care about saving her from wild dogs:

まる子はあまりのことに、思わず箸を落としそうになった。
Maruko almost dropped her chopsticks.

What does あまりのことに mean in this sentence?

I have a grammar book with the formula, あまりのnounに, with the meaning of "because the degree is too high", but all the examples use a noun derived from an adjective (as you would expect given the definition).

Given the above, I guess it just means "at such a thing" / "on hearing such a thing" etc. Could I replace it with something like そんなことで without changing the meaning?

Answer 1

It is something like "such a thing", but あまりのことに does not have much possibility to be replaced by something else (without changing nuances).

あまり means

［形動］［文］［ナリ］
１ 程度のはなはだしいさま。予想を超えているさま。「値段が―に高い」「―な剣幕に恐れをなす」
２ 話にならないほど度が過ぎてひどいさま。あんまり。「―な仕打ちに怒る」

Here it is #2. The closest equivalent in English may be "too much", which I believe is usually negative. So あまりのこと means literally "something that is too much". In the particular context, Maruko thought what she heard just now was extraordinary/outrageous/unbelievable.

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あんまり has a similar usage:

• それはあんまりだ That is too much (e.g. too cruel, too inconsiderate, etc.)