means A toy or shape consisting of curved vanes or spokes radiating from a central pivot, designed to spin when wind or breath catches it — and by extension, anything that whirls or radiates from a center.

from A plain compound of "pin" and "wheel," naming the thing by how it works: a little wheel mounted loose on a pin so it turns freely. "Pin" comes from Old English "pinn" (a peg or bolt, related to Latin "pinna," a feather or point), and "wheel" from Old English "hweol," a cousin of words for turning and circling across the old Germanic and Indo-European tongues. So the name is mechanical honesty itself — the wheel, the pin it spins on, nothing more.