annual (adj.) Look up annual at Dictionary.com
late 14c., "appointed by the year;" c. 1400, ""occurring or done once a year," from Old French annuel "yearly" (12c.) or directly from Medieval Latin annualis "yearly," corresponding to Latin annalis as adjective form of annus "year," which is from PIE *at-no-, suffixed form of root *at- "to go," with Germanic and Latin derivatives meaning "a year," perhaps on the notion of "period gone through" (source also of Sanskrit atati "goes, wanders," Gothic aþnam (dative plural) "year," Oscan akno- "year, holiday, time of offering").
annual (n.) Look up annual at Dictionary.com
c. 1400, originally "service commemorating the anniversary of a person's death," from annual (adj.) or from Late Latin annualem (nominative annualis). By 1680s as "plant that grows again or blooms every year," also as "annual literary publication."