When I was a kid, if I didn't know the name of something, I would give it a name of my own devising.
How many 5 or 6 year olds know that the pointy bits on a fork are called tines, for example? I didn't. So I called them "yay-yays". Probably onomatopoeic in origin. The word's repetition relates to the shape of the object.
How many people of any age would have a word for these things though?
This is one near Thingwall, in central Wirral.
And this one stands proud just outside Bebington Station, also in Wirral.
I think they are old ventilation chimneys for the sewers or drains. They're generally ornamented more than a purely utilitarian approach would allow, with their fluted columns and splayed tops. You don't see that many of them around, but there are a few knocking about.
Anyway, since there doesn't seem to be a definitive noun attached to these things, I propose that they be called Givvies. I've been calling them that for 35 years now, and so do most of the rest of my immediate family.
If anyone reads this and knows the locations of other Givvies (singular: Givvy) feel free to let me know.