It end ups being a word

[Please note that this is a schedule post and I am currently observing my union (UCU)'s industrial action over pensions, pay, workloads, and equality.]

English has a group of verbs that you might know as 'phrasal verbs'. It's things like cheer up, find out, turn off. They include what looks like a preposition (up, out, off) so can be hard to distinguish from normal verbs with a preposition following them. To add to the complication, verbs that are not really phrasal but might have a preposition after them come in two types: they have to have a particular preposition, or they can have any old one optionally. Here's a classic Linguistics 101 example to clarify: 

Look can occur with no preposition at all: 

I'm not sure where it is, I'll look. 

Or it can be followed by one of several prepositions: 

I'm not sure where it is, I'll look at a map. 

I'm not sure where it is, I'll look up the address. 

I'm not sure where it is, I'll look in the atlas. 

I'm not sure where it is, I'll look to the stars as my guide. 

I'm not sure where it is, I'll look with my soul. 

OK, I'll stop there before it gets silly. But one of these is different from the others. Compare these two sentences: 

*I'm not sure where it is, I'll look a map at. 

I'm not sure where it is, I'll look the address up. 

In the second one, we can put the preposition at the end, whereas we can't do that in the first one. That's because look up is (in this case) a phrasal verb, and up isn't really a preposition. It's sometimes known as a verbal particle and it's doing something other than signifying direction. Compare it to the same phrase when it's not a phrasal verb. As we just saw, phrasal verbs like this one can move the 'preposition' to the end: 

I looked up the address.

I looked the address up. 

They can't have any other preposition than the one they go with, though:  

*I looked down the address. 

But if look up is not a phrasal verb, but instead just a normal verb that happens to be followed by a preposition, the opposite is true. You can't move the preposition to the end, but you can change it for another one. (I've added in a bit of context here to make the meaning clear.) 

I looked up the street and saw my friend arriving. 

*I looked the street up and saw my friend arriving. 

I looked down the street and saw my friend arriving. 

Anyway, this is all stuff that's in grammar books, so on to the observational content that you know and love. Someone I follow on twitter used the phrasal verb end up, but treated it as a single unit, putting the verbal ending on the particle, like this: 

...because it end ups reproducing the same situation they want to avoid. 

Normally, you'd expect to see ends up, not end ups. But this does make sense if you consider a phrasal verb to be a single unit. End up is a bit different from look up in that we can't move up anywhere else. It really always does have to be end up, with nothing in between them, and no other preposition than up. The parts don't really mean the same on their own (end could be used in the same way, but it's not). So it's really functioning as a single word in any meaningful sense, and therefore it makes sense to stick the word ending (the 'inflection') on the end of the whole unit, as this person did.