Legendary

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early 16th century (as a noun denoting a collection of legends, especially of saints' lives): from medieval Latin legendarius, from legenda ‘things to be read’ (see legend).

wiktionary

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legend +‎  -ary; from Middle Latin  legendarius. Earlier it was a noun meaning "a collection of legends" (1510s) (Old French legendier), from Latin  legenda. In English, both the noun and the adjective first appeared in the 16th century. 

etymonline

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legendary (adj.)

mid-16c., from Medieval Latin legendarius "pertaining to legends," from legenda (see legend). Earlier in English it was a noun meaning "a collection of legends" (1510s).