1550s, "one newly risen from a humble position to one of power, importance, or rank, a parvenu," also start-up, from up (adv.) + start (v.) in the sense of "jump, spring, rise." As an adjective from 1560s. Compare the archaic verb upstart "to spring to one's feet," attested from c. 1300.
"time limit," 1920, American English newspaper jargon, from dead (adj.) + line (n.). Perhaps influenced by earlier use (1864) to mean the "do-not-cross" line in Civil War prisons, which figured in the trial of Henry Wirz, commander of the notorious Confederate prison at Andersonville, Georgia.
And he, the said Wirz, still wickedly pursuing his evil purpose, did establish and cause to be designated within the prison enclosure containing said prisoners a "dead line," being a line around the inner face of the stockade or wall enclosing said prison and about twenty feet distant from and within said stockade; and so established said dead line, which was in many places an imaginary line, in many other places marked by insecure and shifting strips of [boards nailed] upon the tops of small and insecure stakes or posts, he, the said Wirz, instructed the prison guard stationed around the top of said stockade to fire upon and kill any of the prisoners aforesaid who might touch, fall upon, pass over or under [or] across the said "dead line" .... ["Trial of Henry Wirz," Report of the Secretary of War, Oct. 31, 1865]
It's always neat when a word's etymology basically boils down to "so yeah it literally meant this other thing which it would intuitively mean, but that's been wiped out by a flowery idiomatic use of it to mean that same thing only allegorically instead of literally, to the point that no one even thinks about what the underlying literal meaning of it is anymore."
How old do you think the word "upstart" is?
Spoiler
Shakespeare was even called this by a contemporary theatre critic
jumpscaring me with new knowledge, appreciated
Check out deadline.
It's always neat when a word's etymology basically boils down to "so yeah it literally meant this other thing which it would intuitively mean, but that's been wiped out by a flowery idiomatic use of it to mean that same thing only allegorically instead of literally, to the point that no one even thinks about what the underlying literal meaning of it is anymore."
My guess before I checked was 100 to 150 years.