Keep the good work up / Keep up the good work - Are they both grammatical?
- Keep it up
- Keep up the good work.
- Keep the good work up.
This type of verb plus preposition combination is often called a separable phrasal verb in traditional grammar. It is called this because we can put the complement noun in between the verb and the preposition - or we can put it after preposition. Of course, however, when the complement is a pronoun, it must go in between the verb and the preposition:
- put the pen down.
- put down the pen.
- put it down.
- put down it. (ungrammatical).
However, although we can put the noun phrase complement, either before or after the preposition, we strongly prefer to put long noun phrases after the preposition:
- He rolled the old Venetian rug up. (grammatical but awkward)
- He rolled up the old Venetian rug. (grammatical, not awkward)
This means that, all things considered, we would tend to favour sentence (2) over sentence (3).
As an exhortation to our friends - as an imperative - keep up the good work might be considered a fixed phrase. However, when being used in a normal sentence to keep the good work up is not all that jarring, just a little awkward. It can be seen in published works. You can see it here, for example.
Nonetheless, the good work is a long enough noun phrase for us to strongly prefer to put it at the end of the sentence. Here is an Ngram for keep up the good work versus keep the good work up. (Not that Ngrams should be taken too seriously!):
Actually, "keep the good work up" is flat wrong.
Keep up is a prepositional phrasal verb meaning to continue at the same level or pace (definition from thefreedictionary.com). Unlike particle phrasal verbs, prepositional phrasal verbs cannot be split apart.
Consider the following sentence:
Keep up with me.
You cannot move up away from keep without changing the meaning of the sentence.
Keep with me up.
"Keep up the good work" is not an idiom. An idiom is an expression that cannot be understood from its elements. "Keep tabs on" is an idiom. "Keep up the good work" actually can be understood from its elements.
“Keep the good work up” is not exactly wrong, but neither is it idiomatic English. I think most native speakers would stick with “Keep up the good work”.
Keep up is a general idiom meaning to maintain or stay abreast of.
Keep up speed. (Do not slow down, road sign on gentle uphill.)
Keep up with your homework. (Don't fall behind.)
Keep the good work up is not idiomatic, because we're used to keep up as a unit.
Some discourage the practice of ending a sentence with a preposition (by moving the preposition to the end, in fact).
In this idiomatic expression, the focus is on the phrasal verb keep up and by splitting it, the very essence of the sentiment is lost.
In any case, as already noted in (1) above, the expression keep up the good work (TFD) is an idiom, so use it as it is for the idiomatic effect. Compare: keep it up