Cabin builders use this tool for about the same purpose as a regular chisel. It is about 4" wide, 1 1/2 foot long, and with a 1 1/2-2 foot long handle. What do you call it?
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.
I believe you're describing an ADZE which is a tool used to shape logs: