Please, restrict your answers to etymological info. I browsed some other questions and found some good info here: [Is it correct to change the common structure in these phrasal verbs?](https://english.stackexchange.com/questions/80918/is-it-correct-to-change-the-common-structure-in-these-phrasal-verbs), which is more of a disambiguation question, but it may help answerers on this question. Specifically, this idea: 'The preposition is fused to the verb to create a new, figurative meaning.'

I'm wondering why some verbs have a preposition dangling after the object. I thought it was perhaps because it's expected to connect to an indirect object, but then I found myself adding additional prepositions that sometimes obviate the need for the first one (some examples in square brackets). Example:

> 
> I put some burgers on. Cooked them up. Turned the heat down [*to low*]. Called Nancy up 
>  [*on the phone*]. Asked her if she could come down [*to my house*]. She freaked out. Said 
>  she was down [*to come*]. I passed out. When I came to, she was looking me over.
> 
> 
> She asked, "What knocked you out?"
> 
> 
> "You and I being on," I replied.
> 
> 
> "Let's chow down," she suggested – but I cautioned, "Wait up. Maybe the burgers are burnt up."
> 
> 
> She said, "No. You'd turned the heat down," and pulled two plates out. We scarfed the burgers down and funned around for two more hours before turning in.
> 
> 
> 

I'm basically wondering how words like these developed.