get off

[frindle2]

Hello. Would you please tell me what "get off" means in the context below?
Does it mean 'where do they appear[or start] and always spread out and try to occupy as much of the space as possible?'

(It's story about a boy with Obsessive-Compulsive Disorder. )
My routines fill the hours - the compulsions are like a spilled liquid getting everywhere.
Why do liquids do that anyway? I wonder.
Where do they get off always spreading out and trying to occupy as much of the space as possible?

Source: When I See Blue by Lily Bailey

 

[Barque]

It's a colloquial expression roughly meaning "What do they mean by...?" or "Who do they think they are...?"

Obviously liquids don't think, so it isn't really meant seriously in this context.

It's usually used with people, with the meaning I described above.

 

[teechar]

Where do they get off always spreading out and trying to occupy as much of the space as possible?

Source: When I See Blue by Lily Bailey

If you've quoted that correctly, I would imagine it roughly means "what motivates liquids to spread out and try to fill the surface they're on?"

 

[White Hat]

Also try this: https://idioms.thefreedictionary.com/where+do+you+get+off