Your obedient servant old use
Used to end a letter that is written for an official or important occasion.
It has been a long time I haven't seen any letters that ended with the phrase "your obedient servant."
He wrote at the end of the letter "I beg to remain, sir, your obedient servant." And that seemed weird to me at first because I didn't know that was the old-fashioned way to end a letter.
The origin of this phrase is not clear.