Borrowed from Italian, where it simply means 'biennial' — the word became the global standard for major recurring art exhibitions through the prestige of the Venice Biennale.
A large-scale international art exhibition or cultural festival held every two years, especially the Venice Biennale.
From Italian 'biennale' (biennial, occurring every two years), from Latin 'biennium' (a period of two years), composed of 'bi-' (two, twice) from Latin 'bis,' and 'annus' (year). The word entered English specifically through the Venice Biennale, the international art exhibition first held in 1895. English borrowed the Italian form rather than using its own cognate
The first Venice Biennale in 1895 was conceived as a celebration of the silver wedding anniversary of King Umberto I and Queen Margherita of Italy. It attracted over 200,000 visitors, and the Italian word 'biennale' became permanently attached to the concept of a large international art show — even for events in non-Italian-speaking cities.