Swivel mentioned as meaning a fetter or manacle. Not clear how it meant that.

"swivel - frequentive form from stem of O.E. swifan "to
move in a course, sweep" (a class I strong verb), from
P.Gmc. *swipanan, from I.E. base *swei- "swing, bend,
move in a sweeping manner." M.E. swive was the principal
slang for "to have sexual intercourse."

swivel
n.
ME swiuel < base of OE swifan, to revolve, turn: for IE base see SWIFT6 a coupling device that allows free turning of the parts attached to it; specif., a chain link made in two parts, one piece fitting like a collar below the bolt head of the other and turning freely about it
vt.
3eled or 3elled, 3el[ing or 3el[ling
1 to cause to turn or rotate on or as if on a swivel
2 to fit, fasten, or support with a swivel
vi.
to turn on or as if on a swivel

We had a half dozen posts about "swivel chairs" and "necks swivelling"
Both seem quite a departure from early meaning.

rea chain link made in two parts, one piece fitting like a collar below the bolt head of the other and turning freely about it -- but this is exactly how i would define a swivel, (as a noun)

and swively hips.. still has a very definate sexual connotation!
i have hooks with swivels, and the hooks end in a collar, and a bolt like pieces passes through, and the bolt then is looped, to start a chain.

swivel chairs are just the same thing! a collar, and the bolt that passes through becomes the legs, the collar supports the seat.. (and now days there are ball or roller bearing between the collar and the bolt so things swivel readily.

Dear of troy: Sure, the post of a chair can be kept from coming apart by a swivel,
but everybody thinks about the chair turning.
And how about necks "swivelling"

I have been going nuts for past half hour
trying to remember the name of gadget that hitched plough behind my tractor.
A "C" shaped piece out of ultrastrong forged steel, with tips of "C" having 7/8? holes
through which a strong rod with strong flattened top, and a hole in tapered tip for
small chain to keep it from getting lost. The whole thing was called a clevis.