What is the proper term for a huge chisel-like tool used for building log cabins?
I think you may be talking about a slick:

This is what Wikipedia has to say:

A slick is a large chisel, characterized by a wide (2-4 inches, 5–10
cm), heavy blade, and a long, frequently slender, socketed handle. The
combined blade and handle can reach two feet (60 cm) in length. The
blade of a slick is slightly curved lengthwise, and/or the handle
socket is cranked upward, such that the handle and socket clear the
surface of the work when the edge is touching. This distinguishes the
slick from the similarly-sized, short-handled millwright's chisel.