Jews have many names for God: the Merciful One, Lord, God, the One Who Keeps His Promises, among them.  The pre-eminent name for God consists of the letters Y-H-W-H, sometimes rendered Jehovah or Lord.  Out of respect, the name was uttered only by the High Priest, in the Temple, on the holiest day of the year.  During prayer, it is pronounced Adonai, the translation used in this Haggadah.