Campaign
early 17th century (denoting a tract of open country): from French campagne ‘open country’, via Italian from late Latin campania, from campus ‘level ground’ (see camp1). The change in sense to ‘a series of military operations’ arose from an army's practice of ‘taking the field’ (i.e. moving from a fortress or town to open country) at the onset of summer.
wiktionary
From French campagne, from Italian campagna(“field, military operation”), from Late Latin campānia(“open country, battlefield”), from Latin campus(“field”). Doublet of campagna and champagne.
etymonline
campaign (n.)
1640s, "operation of an army in the field," during a single season, in a particular region, or in a definite enterprise; from French campagne "campaign," literally "open country," from Old French champagne "countryside, open country" (suited to military maneuvers), from Late Latin campania "level country" (source of Italian campagna, Spanish campaña, Portuguese campanha), from Latin campus "a field" (see campus).
Old armies spent winters in quarters and took to the "open field" to seek battle in summer. Generalized to "continued or sustained aggressive operations for the accomplishment of some purpose" (1790); in U.S., especially "political activity before an election, marked by organized action in influencing the voters" [DAE], attested from 1809.
campaign (v.)
"to serve in a campaign," 1701, from campaign (n.). Political sense is from 1801. Related: Campaigned; campaigning; campaigner.
