Original: Twelve dozen (122 = 144, the duodecimal 100) are known as a gross; and twelve gross (123 = 1,728, the duodecimal 1,000) are called a great gross, a term most often used when shipping or buying items in bulk.
Simplified: 12 dozen  (144 items) are a gross, 12 gross (1728 items) are called great gross.