What does CGB mean in reference to a CGB electrical fitting?

"CGB" is a general reference in the Cooper/Crouse-Hinds catalog to various cord and cable stress relief fittings. For example: http://www.crouse-hinds.com/catalog/pdfs/00064to00066_00070to00072.pdf

Other manufacturers make similar fittigs. "CGB" is sort of like "Scotch Tape" is a reference to cellophane tape.

or you could just use "Cable Gripping Bushing" which is a little more understanding.