the.com/hanging valley

means A side valley left stranded high above a main valley floor, its mouth often spilling a waterfall into the larger trough below.

from The term comes straight from geology's plain-English habit of naming what it sees: when a smaller glacier carved a shallower valley into a larger one carved by a bigger, faster-eroding trunk glacier, the smaller valley's floor was left perched well above the main valley after the ice melted — 'hanging' above it rather than meeting it at grade. The phrase itself is a 19th/early 20th-century geological coinage, descriptive rather than borrowed from any older word or myth.