Just ♥ Words — prepositional adverbs

English—what a great language to have fun with!  Here’s a silly little grammatical conundrum for which I have no explanation . . . except that it’s idiomatic.  Nonetheless, rules are rules—and rules must be obeyed.

Don’t You Just ♥ Words?

You can say
Take the garbage out.  —or—  Take out the garbage.
And you can say
Take it out. —but not— Take out it.
___________

You can say
Butter Mom up.  —or—  Butter up Mom.
And you can say
Butter her up. —but not— Butter up her.
___________

You can say
Turn the lights on.  —or—  Turn on the lights.
And you can say
Turn them on. —but not— Turn on them.
  

Verbs and prepositional adverbs—you would think they’re like infinitive verbs—to be or not to be—you’re to never split one of those.  I mean “you’re never to split one.”  (But we all do.)

But prep-adverbs are different from infinitives. If you use a pronoun, you have to split them up”—not  ”split up them.”  Strange.

It's a wonder anyone ever learns English.