Probably everyone else knew already that the Helter Skelter is a slide. I didn't. Even thought -I know- is explicit in The Beatles' lyrics:
When I get to the bottom I go back to the top of the slide
Where I stop and I turn and then I go for a ride
'Til I get to the bottom and I see you again...
I discover that when I get to see one in a couple of Summer Festivals in and around London. For those -if there's any at all- who didn't know about this particular kind of slide, here's a picture of a beautiful Helter Skelter in the Secret Garden Party Festival, and some interesting facts about the origin of the helter skelter according to The Phrase Finder:
Helter-skelter has been in common use in England for the past 400 years and has been known in the USA since the 1820s.
Neither helter nor skelter had any meaning in themselves. Like many word pairs of this sort (called rhyming reduplications), they only exist as part of the pair - although skelter was used alone later, but only as a shortened form of helter-skelter.
Another reduplication with a similar meaning is pell-mell (a confused throng or, in disordered haste). This originated around the same time - the first recorded use dates from 1579. Others which came later, but which are in shouting distance in terms of meaning, are harum-scarum (reckless rowdiness) and hurly-burly (commotion and confusion).