Learn English – How does ‘ask something of somebody’ mean ‘to expect or demand something’

phrase-meaning

I was reading Meaning of “ask of” when I lighted upon this issue:

This meaning of ask (definition 7) is mentioned in the OALD:

7. ask something of somebody =
[transitive] to expect or demand something …

Question 1. I ask not about the definition which I tolerate, but about how to decompose/derive/parse it?
How does the juxtaposition of ask and of effect/imply/induce definition 7?

Update 2014 Jan 17: I wrongly guessed ODO's Definition 3 as the definition of of here. Proof removed.

Best Answer

This is a phrasal verb. Quoted from Wikipedia, (primary source cited from here):

This semantic unit cannot be understood based upon the meanings of the individual parts in isolation, but rather it can be taken as a whole. In other words, the meaning is non-compositional and thus unpredictable.

One must learn the definition of phrasal verbs like one would learn the definition of single words. There are guides that help group them in various ways, but there are lots of exceptions as well.