Authoritative answer
Exact answer
Deadline first referred to a prison boundary that could not be crossed safely; its time-limit sense developed later.
Scope: Recorded English etymology and sense history; reviewed July 31, 2026.
Important boundary: The dictionary dates the English noun to 1864; it does not reduce every early use to one prison site.
Evidence
Quick answer
A short etymology card for deadline: origin, meaning history, memorable hook, and source-language context.
Source-first
Reviewed Sep 2026
Origin story
Originally a prison boundary line; crossing it could mean being shot. Later a time limit.
Why it sticks
The office word used to be a literal line.
Shareable cardDeadline: The office word used to be a literal line.