mortally adverb Extremely, exceedingly, intensely; at all.
c1940 Simms Coll She wuz so mortally glad to see us. 1940 Still Snail Pie 214 Maw did mortally relish partridge. 1955 Ritchie Singing Family 48 I just couldn’t mortally stand to sit still on that log bench and that tune snakin around so. 1997 Montgomery Coll (known to Norris): It’s mortally hot today (Cardwell). 2001 Lowry Expressions 5 My mother-in-law was operated on 3 weeks ago, and she was eat mortally up with cancer.
—Dictionary of Southern Appalachian English
The Deer Hunter uses the word mortally a lot. He might say “He was mortally flying down the road” or “If he wrecks going that fast he’s gonna be mortally wounded” or even “It was mortally hot today.”
Mortally is one of those Appalachian words that are so familiar to me that I don’t think unusual until I run across it in one of my reference books.
Are you familiar with using the word mortally as it’s used in the dictionary entry?