Noun
Gravel Gertie (plural Gravel Gerties)
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
Junior later married Sparkle Plenty (the daughter of B.O. and Gravel Gertie Plenty), and had a daughter named Sparkle Plenty Jr. In the 1990s, Tracy's son Joseph Flintheart Tracy took on a role similar to Junior's in the earlier strips. Source: Internet
O."), along with Gertrude ("Gravel Gertie") Plenty. Source: Internet