The story
From a character in the Dick Tracy comic strip.
Etymology from Wiktionary, CC BY-SA 4.0.
Gravel Gertie
Today it means: A chamber, with a roof covered by a deep pile of gravel, within which nuclear warheads may be maintained; in the event of a (non-nuclear) explosion, the roof is weakened and the gravel falls and prevents the escape of nuclear material Full definition →