Noah Webster
Trepan
TREPAN', noun [Latin tero, terebra, on the root Rp.] In surgery, a circular saw for perforating the skull. It resembles a wimble.
TREPAN', verb transitive To perforate the skull and take out a piece; a surgical operation for relieving the brain from pressure or irritation.
TREPAN, a snare, and trepan to ensnare, are from trap, and written trepan which see.