From The Columbus Dispatch:

Chainsaws were originally invented by Scottish doctors John Aitken and James Jeffray in the last 18th century for medical purposes, specifically to assist in a surgical procedure called symphysiotomy^1^ during childbirth. This early version of the chainsaw was a hand-cranked device used to remove ossified^2^ tissue. Over time, the chainsaw evolved into a powerful tool used for lodging.

1: symphysiotomy, symphysiotomy is a surgical procedure that involves dividing the cartilage of the pubic symphys to widen the pelvis, facilitating childbirth when there is difficulty due to a narrow pelvis. This operation is also called pyelotomy and is performed to allow passage of a baby during obstructed labor. 2 ossified, having turned into bone or bony tissue