English biennium

← Proto-Indo-European *duwo (derived)

← Proto-Indo-European *dwóh₁ (mention)

← Proto-Indo-European *h₂et-no- (derived)

← Proto-Indo-European *h₂et- (mention)

← Proto-Indo-European *-yós (derived)

← Latin biennium (borrowed)

← Latin bi- (mention)

← Latin bis (mention)

← Latin duis (mention)

← Latin duo (mention)

← Latin annus (mention)

← Latin -ium (mention)

→ English year (link)