Understanding why に particle means "because" in this sentence


I am struggling to understand the syntax of this sentence that I found in a
grammar book.

> あまりの言葉 **に** あきれてものが言えませんでした。  
>  I could not say anything because of the outrageously unkind words.

I read it as "not many words に outrageous thing が was unable to speak."  
In other words, the pattern used to say "because of B I was C(action) A" would
be "AにBがC(action)." Is this the correct understanding of this grammar?




The に doesn't really mean 'because' there. It's just the particle the verb
あきれる takes. You're making the mistake of trying to parse beyond sentence
boundaries.

The basic structure of the sentence is that there are two clauses, which are
joined by the て form.

Sentence 1:

> あまりの言葉にあきれて
>
> _Shocked by (someone's) overly harsh words_

Sentence 2:

> ものが言えませんでした。
>
> _I was at a loss for words_

The て form when joining two sentences sometimes implies reason: 「明るくて、眠れない」
_it's so bright that I can't sleep_

And it is the て form joining the two sentences that carries the connotation of
'because'.

> _I was so shocked by [his] excessive harshness **that** I couldn't speak_

By the way, ××にあきれて、ものが言えない returns quite a few results on a web search and
seems to be somewhat of a fixed phrase. Here's a sample from 研究社 新和英中辞典

> 彼のばかにはあきれて物が言えない。
>
> _His stupidity really staggers me._

