yy

Alternative forms

 * (four-digit)

Noun

 * 1)  (in two-digit numeric format, as in: dd/mm/yy)

Etymology 1
Possibly from, but more likely formed by analogy to the other names of vowel letters.

Etymology 2
<, specifically the initial syllable

Numeral

 * 1)  one

Noun

 * 1) water