An 1823 dictionary describes a sandboy as an urchin who sold sand in the streets and according to the same source the expression jolly as a sandboy was already proverbial by
that date for a merry fellow who has tasted a drop. A common British version of the phrase is happy as Larry, Larry being a pet name for Lawrence. This saying is sometimes connected with the renowned boxer Larry Foley (1847-1917). On the other hand, it may owe something to larry, a dialect word used by Thomas Hardy, meaning a state of excitement. The North American version is happy as a clam which apparently originated in the early 19th century on the east coast where clams are plentiful : the full version happy as a clam at high water explains the source of the clam's satisfaction.