How did 逸 come to feature in pleasure/idleness words? I can't judge the reliability of < (and it is probably controversial), but there the speed, movement meaning of is linked to its claimed origins in {. Hence , and such that involve some form of movement. However, there are also words like , that are linked to pleasure, idleness etc. Where does this meaning come from?

Kanji dictionaries () are what to look up when confronting questions like this. From what I've got from my dictionary:

* My dictionary states actually is linked to in origin: "rabbits run away" -> to run, to astray.
* For and others, it states that they are used (in modern usage) in substitution for "", whose phonetic value is also "". So was originally "" has no kunyomi, and its meanings include " (to enjoy/have fun)", " (to be idle)". comes from +, and according to the dictionary, the origin is "", so perhaps it is a good substitute even when considering the meaning.