deadline

Etymology

Formed from English dead + line.^[1][2] The sense “time limit” is recorded by 1919 in American newspaper jargon, specifically the last moment at which copy could be sent to the printer.^[1] It was perhaps influenced by an earlier sense (1864): the line in American Civil War prisons that prisoners were forbidden to cross, as at the Confederate prison at Andersonville, Georgia.^[1] Wiktionary notes that the evidence for this connection is only indirect,^[3] and that earlier uses, according to the OED, refer to lines that do not move, such as in angling.^[3]

References

1. [1] [2] [3] Harper, Douglas, Online Etymology Dictionary, https://www.etymonline.com
2. [1] Random House Webster's Unabridged Dictionary, New York: Random House
3. [1] [2] Wiktionary, the free dictionary, https://en.wiktionary.org