Official
Middle English (originally as a noun): via Old French from Latin officialis, from officium (see office).
wiktionary
From Middle English official, from Old French official, from Latin officiālis, from Latin officium(“duty, service”).
etymonline
official (n.)
early 14c., "minor ecclesiastical court officer" (mid-13c. as a surname), from Old French oficial "law officer; bishop's representative" (12c.) and directly from Late Latin officialis "attendant to a magistrate, public official," noun use of officialis (adj.) "of or belonging to duty, service, or office" (see official (adj.)). From mid-14c. as "a domestic retainer in a household;" the meaning "person in charge of some public work or duty, one holding a civil appointment" is recorded from 1550s.
official (adj.)
late 14c., "performing a service" (a sense now obsolete); c. 1400, "required by duty," from Old French oficial "official; main, principal" (14c., Modern French officiel) and directly from Late Latin officialis "of or belonging to duty, service, or office," from Latin officium "service, kindness, favor; official duty, function, business; ceremonial observance," literally "work-doing," from ops (genitive opis) "power, might, abundance, means" (related to opus "work," from PIE root *op- "to work, produce in abundance") + combining form of facere "to make, to do" (from PIE root *dhe- "to set, put").
Meaning "pertaining to an office or official position" is from c. 1600. That of "derived from the proper office or officer," hence "authorized," is by 1854.
