deadline (n.)youdaoicibaDictYouDict
"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 Wirz trial.
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 across the said "dead line" .... ["Trial of Henry Wirz," Report of the Secretary of War, Oct. 31, 1865]
hobnail (n.)youdaoicibaDictYouDict
1590s, the first element probably identical with hob "rounded peg or pin used as a mark or target in games" (1580s), of unknown origin. See hob. Because they were used to make rough shoes, the word was used figuratively for "rustic person" 17c. and after. Related: Hobnailed.
nail (v.)youdaoicibaDictYouDict
Old English næglian "to fasten with nails," from Proto-Germanic *ganaglijan (cognates: Old Saxon neglian, Old Norse negla, Old High German negilen, German nageln, Gothic ganagljan "to nail"), from the root of nail (n.). Related: Nailed; nailing. Meaning "to catch, seize" is first recorded 1766, probably from earlier sense "to keep fixed in a certain position" (1610s). Meaning "to succeed in hitting" is from 1886. To nail down "to fix down with nails" is from 1660s.
pig (n.)youdaoicibaDictYouDict
probably from Old English *picg, found in compounds, ultimate origin unknown. Originally "young pig" (the word for adults was swine). Apparently related to Low German bigge, Dutch big ("but the phonology is difficult" -- OED). The meaning "oblong piece of metal" is first attested 1580s, on the notion of "large mass." Applied to persons, usually in contempt, since 1540s; the derogatory slang meaning "police officer" has been in underworld slang since at least 1811.
The pigs frisked my panney, and nailed my screws; the officers searched my house, and seized my picklock keys. ["Dictionary of Buckish Slang, University Wit and Pickpocket Eloquence," London, 1811]
Another Old English word for "pig" was fearh, related to furh "furrow," from PIE *perk- "dig, furrow" (source also of Latin porc-us "pig," see pork). "This reflects a widespread IE tendency to name animals from typical attributes or activities" [Lass]. Synonyms grunter, porker are from sailors' and fishermen's euphemistic avoidance of uttering the word pig at sea, a superstition perhaps based on the fate of the Gadarene swine, who drowned. The image of a pig in a poke is attested from 1520s (see poke (n.3)). Flying pigs as a type of something unreal is from 1610s.