1650s as a stand-alone adjective; also used as an adverb and noun in 17c. (see extra-); modern usages -- including sense of "minor performer in a play" (1777) and "special edition of a newspaper" (1793) -- probably all are from shortenings of extraordinary, which in 18c. was used extensively as noun and adverb in places extra would serve today.
he always carried extras in case of an emergency
extra ribs as well as other supernumerary internal parts
found some extra change lying on the dresser
an extra pair of shoes
need extra help
an extra fast car
extort
extortion
extortionate
extortionist
extra-
extra
extract
extraction
extra-curricular
extradite
extradition
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