The Word Damn, Damned, is English. Olde English, to be precise.

That word(s) appear exactly zero times in the Hebrew and Greek texts as received.
The Greek words that appears new Testament which the KJV interpret either 'damn', or 'damned' are either Strongs # 2632 or 2919.

2632 appears 21 times. It is interpreted 'damned' twice.

2632 katakrino (kat-ak-ree'-no);

from 2596 and 2919; to judge against, i.e. sentence:

KJV-- condemn, damn.

2919 appears 119 times. It is interpreted 'damned' only once.

2919 krino (kree'-no);

properly, to distinguish, i.e. decide (mentally or judicially); by implication, to try, condemn, punish:

KJV-- avenge, conclude, condemn, damn, decree, determine, esteem, judge, go to (sue at the) law, ordain, call in question, sentence to, think.

Other kindred words, interpreted in the KJV as damnation.. a total of 11X are the following:

2917 krima (kree'-mah);

from 2919; a decision (the function or the effect, for or against ["crime"]):

KJV-- avenge, condemned, condemnation, damnation, + go to law, judgment.

265 hamartema (ham-ar'-tay-mah);

from 264; a sin (properly concrete):

KJV-- sin.

2920 krisis (kree'-sis);

decision (subjectively or objectively, for or against); by extension, a tribunal; by implication, justice (especially, divine law):

KJV-- accustion, condemnation, damnation, judgment.

684 apoleia (ap-o'-li-a);

from a presumed derivative of 622; ruin or loss (physical, spiritual or eternal):

KJV-- damnable (-nation), destruction, die, perdition, X perish, pernicious ways, waste.

So, the words God Damn are literally a COMMAND to God to condemn it. it is in deed 'vain' for a man to command God.

And that is the sin. the O T English 'in vain' is Strong's

7723 shav' (shawv);
or shav (shav); from the same as 7722 in the sense of desolating; evil (as destructive), literally (ruin) or morally (especially guile); figuratively idolatry (as false, subjective), uselessness (as deceptive, objective; also adverbially, in vain):

KJV-- false (-ly), lie, lying, vain, vanity.

7722 show' (sho);

or (feminine) show'ah (sho-aw'); or sho'ah (sho-aw'); from an unused root meaning to rush over; a tempest; by implication, devastation:

KJV-- desolate (-ion), destroy, destruction, storm, wasteness.

Thus literally, when one uses the phrase God Damn, it is not a request or prayer. It is rather a command, such that the utterer is stating he knows the judgement of the thing.

Clearly man can have a fairly good idea of how God will judge based on written history. But vanity wishes it in mans own time and on his say so. But time is a part of God's judgement we do not know. Therefore main is not the judge, nor the judges boss.

Consider Jonah and Job. Then consider the equivalent 'God Damn's' made by numerous prophets.. "Let (may) God judge the thing (between you and I). That is a request, not a command.

Though many know the intent of POTUS' words, and no way do they assume he meant to 'command' God. Yet, that is exactly what he did.

No doubt he would have been much better served by stating... "We sincerely pray that God will condemn those words and actions".

And, his mistake did cost him....votes. Paul illustrated this concept well in Corinthians, when he taught to 'be careful that your freedom in Christ not cause a weaker brother to stumble'.

The same spring cannot yield both sweet water and salt water. That's a hard thing to learn by zealous Christians.