Tetragrammaton
A word from Greek meaning “four letters.” It refers to the four consonants of the biblical name of God, Yahweh, YHWH. From ancient times it was considered too sacred to be pronounced, and Adonai was substituted for it. The Prayer Book Psalter and the King James OT rendered the name of God “Lord,” and the 1979 BCP continues this usage with YHWH rendered in capital and small capital letters: Lord (BCP, p. 583).
Glossary definitions provided courtesy of Church Publishing Incorporated, New York, NY,(All Rights reserved) from “An Episcopal Dictionary of the Church, A User Friendly Reference for Episcopalians,” Don S. Armentrout and Robert Boak Slocum, editors.