Abbrivated "yud yud" in Hebrew texts. Not to be read aloud without having one's head covered out of respect for adonai. See also: Hebrew words for god. As used in:
Baruch Atah Adonai Eloheinu Melech ha-olam borei p'ri hagafen.
Translation:
Blessed art Thou O Eternal our God, ruler of the Universe, who creates the products of the vine!
This is the kiddish over sedar wine.