The Edible Geography blog has an entry featuring scrimshaw pastry tools on exhibit at the New Bedford Whaling Museum. She calls these "pie crimpers" and theorizes on the diversity:

"The exhibit attributes this functional extravagance to many hours of boredom at sea, but also to the American diet in the nineteenth century. A typical New England meal of the era would involve not just pie, but pies, in both savoury and sweet form. Armed with a crimping multi-tool, a lucky whaler's spouse or mother need never fear a moment's confusion differentiating between her cherry and chicken pies."

If I google on "pie (or pastry) crimper" some of these and their modern versions come up. But, I think that these are (mostly) better labelled as "pastry cutters". In the pie/pastry context, I defined "crimp" as pressing together layers of dough to seal them together, usually with some decorative flourish.

If you want to make a lattice-top pie, you can use these cutting wheels like a pizza cutter to make the strips of dough -- with pretty zig-zag edges. Here is an edge-on view that shows the cutting edge more clearly.

You can also make fancy edges on cookies/biscuits like this, or cut apart filled dough (e.g. ravioli) like this. (You seal the layers together by wetting and pressing, though. The tool just cuts.)

In all the how-tos that I've seen (in books or online), I've never seen one of these wheeled tools used for pressing layers of dough together to seal them.

In the Google search, I do find this and this type of wheeled-tool, which does fit my idea of a tool that can be used to press together layers of dough to seal the edged of a closed pie, or decorate the edge of a single-crust pie. Here's a lovely and detailed Victorian ad: the crimping wheel also cuts (with a straight edge) simultaneously -- but the little zig-zag cutting wheel is used for some other purpose.

Another type of result for "pastry crimping tool" is a pair of small, toothed tongs that can be used to pinch dough together for a decorative effect. Also these and these.

I do see crimping as a function of the non-wheel portion of this scrimshaw and this brass and this multi-tool: used to pinch dough against fingers or a pan, they would do the trick in a decorative way.

The definition of "crimp" is "compress (something) into small folds or ridges" (Oxford American English). Are people expanding that definition to any zig-zag, even if it's cut, rather than compressed?

Or is it just that there are a lot of people who have never actually used these tools making labels for them? :-)

~ Becky in Long Beach
(is it obvious that I have time on my hands at the moment? The scrimshaw is lovely.)