Green’s Dictionary of Slang

damn v.

also dam, dom
[SE damn, to send to hell; the term is not sl. per se, but as cited by the OED is ‘used profanely’ and (in late 19C and beyond, still often found as d--n or even d---); thus it qualifies]

1. [late 16C+] an all-purpose profanity, used in a wide variety of contexts.

2. as past participle of sense 1; usu. as damned if... or ...be damned (cf. I’ll be damned! ).

In phrases

as be damned (adv.)

[mid-19C+] a general intensifier, extremely, very, to a great extent.

damn-your-eyes (adj.) (also damn-my-eyes)

[mid-19C–1930s] provocative.

In exclamations

damn me for a horse if I do!

[early 19C] an excl. implying one’s absolute refusal to do something.

damn (someone’s) eyes!

[mid-18C+] an excl. of irritation, impatience, annoyance etc., also used attrib.

I’ll be damned! (also damnify! I’ll be damn! I’ll be double damned! I’m damned!)

[mid-18C+] an excl. of annoyance, surprise, irritation etc.