Bogard, 37, of Oak Park, said he tried to settle with the village but was unsuccessful. Now he is suing village officials and the Fire Department for damages. "They basically told me to pound sand," he said recently, standing outside the two-story home on the otherwise tidy 800 block of Forest Avenue.... from Man accuses Oak Park of trashing home by Erin Meyer

I've used this expression myself, but never stopped to think about what exactly it means until seeing this story.

WordOrigins.org cites the Oxford English Dictionary and reports:

The expressions "go pound sand" and "not enough sense to pound sand" are American slang from the 19th century. It is a reference to menial, and often pointless, labor....The latter phrase often appears in a longer form, "not enough sense to pound sand down a rathole." This appears somewhat later.

At Quora.org, lexicographer Jonathon Green, author of several reference books about slang, writes:

There are two takes on go pound sand. The more recent, seemingly a product of World War II, and often euphemised, is go pound sand up one's (rear end). It is used to dismiss and deride, and is ultimately a vehement way of saying: "go away"...A variant meaning is to suffer or to act in a pointless manner:

1974 G.V. Higgins Cogan’s Trade (1975) 14: I was pounding sand up my (rear end) almost four years.

The late 19th century phrase "pound sand in a rathole" originated on campus and meant to be reasonably intelligent. It was usually found in the negative phrase, "not enough sense to pound sand in a rat hole."

The Phrase Finder says "There's also a less vulgar version, 'go pound sand in your ears'."

Several other sites note that "salt" and "sand" seem to be interchangeable when it comes to the more anatomically graphic version of the expression.

In 2002, New York Times language maven William Safire mused on the expression:

"Pound sand" has escaped its earlier scatological association. Along with "go pound salt," the imperative now has the dismissive sense of ''buzz off; go jump in the lake''; it has lost its taboo connotation of ''do something humiliating to oneself."...

When Clark Clifford in the last days of the 1948 election campaign told his boss, President Harry Truman, that a Newsweek poll of 50 reporters gave him no chance of beating Tom Dewey, the man from Independence replied: ''I know every one of these 50 fellows. There isn't one of them has enough sense to pound sand in a rat hole.'' ....the sense that is now becoming predominant, replacing stupefying stupidity, is ''wasting time by doing something pointless."

So pounding sand used to be a good thing -- a sensible task undertaken by a person wise in the ways of rodent control -- until it became a bad thing -- a painful act of self-abasement -- and then morphed into a simple act of futility.