Before the adoption of #ArabicNumerals into Hebrew script, the standard way to write numbers in Hebrew was with #HebrewNumerals, which work much like #LatinNumerals (y'know, V = 5, X = 10, so XV = 15). Rather than separate number symbols, numerical values were assigned to letters of the alphabet. Writing numbers meant writing a particular string of letters.

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Tu B'Av = "fifteen in Av" (i.e. `5th of Av)

But the Hebrew word for 15 is chamisha-'asar (literally "five-ten") so what's "tu"?

Before the adoption of #ArabicNumerals into Hebrew script, the standard way to write numbers in Hebrew was with #HebrewNumerals, which work much like #LatinNumerals (y'know, V = 5, X = 10, so XV = 15). Rather than separate numerical symbols, numerical values were assigned to letters of the alphabet. Writing numbers meant writing a particular string of letters.
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#bet (#beis, #beth, etc) /bet (Hebrew), beɪt (Jewish English)/ = 1. 2nd letter of the Hebrew alphabet, representing the sounds /b/ and /v/; 2. the number TWO (2) in #HebrewNumerals

#YudBet (also #YodBet, etc) = 10 + 2 = 12 in Hebrew numerals

Yud Bet Christmas = "12 Christmas" [twelfth day of Christmas]

#Erev /ˈerɛv/ = 1. evening, 2. when preceding a day/holiday/time period, the day before the specified time period.

#ErevEpiphany = "Eve (of) Epiphany"

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#yod (#yud, #jod, etc) = 1. 10th letter of the Hebrew alphabet, representing /j/ (usually spelled <y> in English, as in YES) or /i/ (= EE vowel); 2. The number TEN (10) in #HebrewNumerals

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