Although corned beef has been around since the Middle Ages, its name was aquired in the 17th century, from the corns of salt used to preserve it; in Europe, "corn" means grain, so this is meat preserved with grains of salt (a similar use is found in the word peppercorns). Corned beef originated in Ireland in the Middle Ages; the Irish didn't eat it, instead shipping it to England and Europe, where it was valued because it didn't spoil. The Irish ate bacon instead of corned beef because pigs were easy to raise (they mostly ran wild until butchering time) and therefore cheap, while cattle were expensive and highly valued for their milk products.
Over the centuries, corned beef became the travel food of choice for European governments. The French shipped it to their sugar colonies in the Caribbean for use as as cheap, durable food for slaves. The British Navy used it for sailors, who introduced it to Pacific Islands (this sounds similar to Spam's position in Hawaii). The islanders had salt readily and cheaply available, so they promptly learned how to make corned beef and other salted foods themselves and sold it to ships stopping in port to resupply.
Corned beef continued its international travels in South America in the 19th century, which had a glut of poor-quality beef. South Americans solved this problem by canning corned beef for export; by the end of the century, their canneries supplied vast amounts to US and European militaries. The British army used large amounts of canned corned beef in WWI and WWII because soldiers could eat it cold straight from the can; there it came be be known as "bully beef", from French bouilli (boiled).
Corned beef doesn't appear to be eaten much by the Irish still in Ireland; they prefer their bacon. When they do eat beef, they prefer spiced beef, which starts out like corned beef but then undergoes another spicing and steeping period before being eaten cold. Irish-Americans picked up the habit of eating corned beef in New York after the potato famine, when beef was cheaper than pork; they may have acquired the taste from their Jewish neighbors.
Although my daughter insists that I make corned beef today, I prefer to avoid the cabbage part of the traditional American dish, probably as a result of too many corned beef and cabbage hot lunches when I was in school. I get freshly corned beef from my local Meat Shop (no spice packet) and braise it all afternoon, then serve it with baby red potatoes topped with goat cheese, and a green salad - my compromise between tradition and taste. Tomorrow or the next day, I will look forward to making corned beef hash for the first time (if I have any left-overs). Maybe next year I will try "corning" my own...
Simple recipe for corned beef hash:
4 large potatoes, peeled and diced
1 pound corned beef, diced
1 large onion, chopped
1 cup broth from cooking corned beef
In a large deep skillet, over medium heat, combine the potatoes, corned beef, onion, and broth. Cover and simmer until potatoes are of mashing consistency, and the liquid is almost gone. Mix well, check seasonings, and serve.
Sources: Salt: A World History, by Mark Kurlansky
Pickled, Potted, and Canned, by Sue Shephard