2236: Why Tu BShvat is called 'Tu' Jan 28, 2021

The Jewish holiday of Tu B'Shvat—which just ended if you read this at the time of publication—is named for the date: the 15th of the month of Shvat (שבט‎). 'Tu' (ט״ו) is not a number however though it is seen here and also in the holiday Tu B’Av. Indeed, Hebrew uses a quasi-decimalized numerical system for writing numbers based off the order of the alphabet, as with Greek numerals, but while numbers from ten (י), eleven (יא or 10+1), twelve (יב or 10+2) etc. just go in order that way with addition, 15 and 16 are represented ט״ו‎‎ (9 + 6) and ט״ז‎‎ (9 + 7) as to avoid writing out one of the spellings for a name of Gd. It just so happens טו would be pronounced 'tu', but in normal speech the word would be חמש-עשרה (chamesh-esre).