Hostage
Middle English: from Old French, based on late Latin obsidatus ‘the state of being a hostage’ (the earliest sense in English), from Latin obses, obsid- ‘hostage’.
wiktionary
From Middle English hostage, ostage, from Old French hostage, ostage. This, in turn, is either from Old French hoste(“host”) + -age (in which case the sense development is from taking someone into "lodging" to taking them into "captivity", to applying the term to a captive), [1] or is from Vulgar Latin obsidāticum(“condition of being held captive”), from Latin obses(“hostage, captive”), with the initial h- added under the influence of hoste or another word. [2] Displaced native Old English ġīsl.
etymonline
hostage (n.)
late 13c., from Old French ostage, hostage "kindness, hospitality; residence, dwelling; rent, tribute; compensation; guarantee, pledge, bail; person given as security or hostage" (11c., Modern French ôtage), which is of uncertain origin. Either from hoste "guest" (see host (n.1)) via notion of "a lodger held by a landlord as security" [Watkins, Barnhart]; or else from Late Latin obsidanus "condition of being held as security," from obses "hostage," from ob- "before" + base of sedere "to sit," with spelling influenced by Latin hostis. [OED, Century Dictionary]. Modern political/terrorism sense is from 1970.
