Tom, one of the advantages of having your suggestion languish in the in-tray for years is that a word that wasn't in the dictionaries may have been included by the time your suggestion is evaluated. Maybe that's happened here. At any rate,
gerb is now present in the online Merriam-Webster and Wiktionary. Both dictionaries identify it as an alternate spelling for
gerbe, which has a few other meanings, apart from the variety of firework.
Gerbe is already accepted in Chi, but since the alternate spelling
gerb is acknowledged by dictionaries, and is in use, as revealed by Google, I'll add that version to our list.
The word comes from the French word for a wheat sheaf. The
OED quotes the 1886 edition of the
Encyclopedia Britannica:
Gerbes are choked cases, not unlike Roman candles, but often of much larger size. Their fire spreads like a sheaf of wheat.