The Tetragrammaton

For centuries devout Jews have refrained from pronouncing the proper name for God given in the Tanakh, or what Christians call the Old Testament. In roman letters the Tetragrammaton, or the four-letter name, is sometimes rendered as YHWH. In the more remote past it was sometimes rendered incorrectly as Jehovah, as in the American Standard Version of the Bible published in 1901. It seems the Tetragrammaton has not been pronounced for so long that no one knows its actual pronunciation. The Jerusalem Bible and New Jerusalem Bible speculatively fill in the vowels, thus making it Yahweh. For centuries, whenever YHWH is encountered in Hebrew, the reader substitutes Adonai, or Lord.

Something has puzzled me about all this: if Jewish believers refrain from pronouncing YHWH, why then are they willing to pronounce it when it occurs in proper names, as in, e.g., Elijah ("YHWH is God") or Adonijah ("YHWH is Lord")? If anyone knows the answer to this, I'd love to hear it.