Chainsaws Were Originally Invented To Assist With Childbirth
If you think expelling an entire additional human from your body is a miserable experience, you're right, but it could be even more miserable. Back before C-sections were common, and death didn't seem like a desirable alternative to having one, if a baby was having trouble getting out, doctors went in and cut out some bones and cartilage to make room for it in a procedure called a symphysiotomy. Here's a visual (the "5" area is what was cut). It's still not totally clear what's going on, but you get the horrifying picture.
It took a long time with a simple scalpel, which neither the patient in unimaginable pain nor the busy doctor liked. In the late 18th century, two Scottish surgeons remedied the situation by employing a "modified knife with serrated 'teeth' on a chain" to speed up the process. In the procedure, "the doctor would grab the saw, which had a handle on both ends, and wrap the chain around the pelvic bone, pulling each handle so the chain would cut into the bone." This was regarded as the "more precise and humane option."
By 1830, the chainsaw was modified to be more generally functional during surgery. Again, it was actually considered an improvement for your doctor to start waving a chainsaw at you like an altruistic Leatherface because the resulting wounds healed better than when they used the standard tools of the trade, i.e., cleavers and axes.
It took another 30 or so years before someone realized that a really big one of those guys could be used for cutting wood. What's that old lumberjack expression? "This forest's like a great big elbow just waiting to get amputated"?