Q: This one may be easy for you, but quite a few other people don’t know which of these forms is correct: “I have to cut down that damned tree” or “I have to cut down that damn tree.” What’s your verdict?
A: Both sentences are correct.
The Oxford English Dictionary (a damn good dictionary and pretty damned authoritative) says “damn” and “damned” can be either adjectives or adverbs.
Merriam-Webster’s Collegiate Dictionary (11th ed.) agrees. M-W says either word can be an adjective (as in “a damn/damned shame”) or an adverb (as in “a damn/damned good job”).
The OED says these adjectives and adverbs are derived from the verb “damn,” which English borrowed from Old French around the year 1300. The ultimate source of the word is the Latin verb damnare, meaning to inflict damage or condemn.
That damn near sums it up, dammit (which the OED defines as a version of “damn it”).