chain (n.) Look up chain at Dictionary.com
c.1300, from Old French chaeine "chain" (12c., Modern French chaîne), from Latin catena "chain" (source also of Spanish cadena, Italian catena), of unknown origin, perhaps from PIE root *kat- "to twist, twine" (cognates: Latin cassis "hunting net, snare").

Figurative use from c.1600. As a type of ornament worn about the neck, from late 14c. Chain of stores is American English, 1846. Chain gang is from 1834; chain reaction is from 1916 in physics, specific nuclear physics sense is from 1938; chain mail first recorded 1822, in Scott, from mail (n.2). Before that, mail alone sufficed. Chain letter recorded from 1892; usually to raise money at first; decried from the start as a nuisance.
Nine out of every ten givers are reluctant and unwilling, and are coerced into giving through the awful fear of "breaking the chain," so that the spirit of charity is woefully absent. ["St. Nicholas" magazine, vol. XXVI, April 1899]
Chain smoker is attested from 1886, originally of Bismarck (who smoked cigars), thus probably a loan-translation of German Kettenraucher. Chain-smoking is from 1930.
chain (v.) Look up chain at Dictionary.com
late 14c., "to bar with a chain; to put (someone) in chains," also "to link things together," from chain (n.). Related: Chained; chaining.