What is this tool?

Wrench in the US, spanner elsewhere.

Kind of atypical. But I'd call it a "Plumber's Wrench"

I've never seen one before, but I did a reverse image search and it comes up as a "flume wrench".

When I worked as a plumber in Canada we called it a faucet tool. They’re usually specific to the brand/faucet.

"Tube spanner" or "tubular spanner"

I'm sure it is not something to be placed in the butt

Looks like a socket spanner of some sort?

Thanks for the comments! I'll use it just once, so I thought about 3D printing it. I looked for a ready-made model, but I couldn't get any results from traditional searches.

Definitely some kind of wrench

I don't know what this is called in my own language I don't even know what this is