A nice companion-piece to Dave’s entry by Joanna Rubery, an online editor at Oxford University Press.
Leap years around the world
The etymology of the slightly puzzling English term leap year is uncertain, but it’s thought that the name originated in late Middle English. But other languages use different terms: in German (Schaltjahr) and Chinese (闰年(rùnnián)) , the terms used literally translate as the more technically accurate intercalary year. On the other hand, the Romance languages and Russian use année bissextile (French), anno bisestile (Italian), año bisiesto (Spanish), and високо́сный год (Russian), terms that derive from the Latin bis sextum (bissextile or “second sixth” in English), due to the fact that in a Roman leap year, the sixth day before March calends (sextum) was counted twice (bis). In Reggio Emilia in northern Italy, a leap year can also be referred to as l’ann d’ la baleina (in dialect), literally the whale’s year, according to the belief that whales give birth only during leap years.
I’m instantly enamoured of the term whale’s year. One wonders how this odd belief arose.