Various simple sentences occur in English that I can't explain precisely.
"In we went!" "Off he goes!"
Is this an arcane idiom from an earlier grammar, or is there a general rule that can be abstracted here?
Edit: initially I thought "in" was a preposition but I realise now this is a behaviour of particles.
"Up he looked" Although for transitive verbs this seems to not work: *"Up he picked"
It seems that the particle may move to the immediate left of the subject but no further, for example:
*Up, Mary saw John eat
Additionally it isn't possible to substitute it for a normal VP:
*Mary saw up John eat.
Has this been investigated further?