Whirligig as applied to this type of toy was in use by the seventeenth century, according to the OED, and this type of artifact is common in eighteenth-century contexts, according to Ivor Noel Hume (A Guide to Artifacts of Colonial America, 1970, 320-321) and others. I think the term "whizzer," although common among archaeologists and the public, may be anachronistic, as I've been unable to locate its origin or a period reference.
I was wondering in particular why some are round and others have teeth around their edges. So, I got to work with a few basic tools - a knife, a plain file, and a rat tail file for smoothing out the cut holes. For my whirligigs, I used some old (reproduction) Revolutionary War British army buttons.
Tools and raw material (pewter button) atop a page from Lynn L. M. Evans's Keys to the Past: Archaeological Treasures of Mackinac (2003, 41) showing an original whirligig and an illustration of one in use.
It takes less than half an hour to turn a pewter button into a toothed whirligig. That involves filing off the shank, piercing holes by twisting a knife around in a precise spot, and filing the teeth around the edge. The pewter buttons I used are harder than lead, so original whirligigs made from repurposed lead cloth bale seals or flattened musket balls would have been even faster to make.
I made four whirligigs, each with minor variations, to test whether any particular type worked better or made a louder noise. I assumed the teeth had something to with the noise factor.
Some experimental whirligigs.
I had expected these toys to whine or hum when spun. In fact, the toothed ones actually only make a fine rushing sound (a whizzing sound, in fact). The one without teeth is silent when spun, except for the sound of the string twisting (which is actually relatively noisy). I can't discern any difference in sound between the fine-toothed and coarse-toothed examples. The one in which I drilled holes far apart (at the bottom of the above image) also works, but it's harder to start and keep spinning than the others. Some excavated whirligigs have a third, central hole, but I'm still at a loss to explain that. I'd be happy to hear from anyone who has an idea. In the mean time, I'll be playing with these entrancing little toys.
After reading this and mastering the whirligig herself, the ever-astute Nicole Belolan asked what it was about the whirligigs that made them "fun." She speculated that it has more to do with the unique physical sensation of the tensing and loosening string than with any sight or sound. We live in a world filled with visual and auditory entertainment, and toys that entertain us through the sense of touch are relatively uncommon, at least once we move beyond infancy. Nicole also speculated about whether early American children might have competed to see who could keep their whirligig going the longest, as their hands and arms grew tired from the work, in the same way that more recent children compete at dribbling balls or spinning hula hoops.