https://github.com/davepinch/pinchy.cc/blob/master/content/topics/religion/christianity/bible-books/psalm/chapters/psalm-137/verses/psalm-137-9/psalm-137-9-kjv.md
Tarn (lake) (Wikipedia) A tarn (or corrie loch) is a mountain lake, pond or pool, formed in a cirque excavated by a glacier. A moraine may form a natural dam below a tarn.
O daughter of Babylon, who art to be destroyed; happy shall he be, that rewardeth thee as thou hast served us. Psalm 137:8 KJV