nichts von alledem-what is "alledem"

Question

Here is a sentence:

Immer noch war er entschlossen, nichts von alledem seiner Frau zu sagen.

I'm curious about this "alledem". Is this some form of "alle" or a completely different word?

Answer 1

It's a fixed expression, but derived from "das alles" / "alles das", hence in the dative case "all(...)dem" (the first inflection got lost).

You can look up all such things: https://de.wiktionary.org/wiki/alledem with more links there.