A mackinaw is a short woolen coat, favored by those who, like loggers, spend time in the snowy forests of Maine, Upper Michigan, and the Pacific Northwest. There is one made by Filson (one of the traditional mackinaw makers) pictured here http://smtp2.thewwwstore.com/filson/85.HTM
but they have evolved over the years and now come in other designs.

Down har in Kaintuk, we'uns call em "britches." Like in, "Joe Bob, git yet britches on! The catfish are a-callin'!" Mind you, I only live here; back where I grew up we called such garments "pants" "trousers" "britches" and/or "jeans." I've also heard them called "trews" and "breeches."

Gentlemen do not discuss nether garments in public forums....