Forklore: Boards that really do groan
The closer we get to Thanksgiving and Christmas, the more we hear heavily laden dinner tables referred to as groaning boards. This is sort of cute and poetic, although of course it's basically true that a table (whether groaning or not) is a board mounted on legs.
But the real reason for this expression is that "board" was the original word for table in English. What we call tables--boards with permanently attached legs--existed in the Middle Ages; there were worktables, for instance. But people didn't eat off them, at least when they had company. They constructed a dinner table by setting a board on sawhorses.
One reason was that until recent centuries, most rooms in a house did not have a set purpose. There was no bedroom and separate dining room, for instance. At dinner time, you just rolled up your mattress and bedclothes and stashed them in a corner, then unfolded the sawhorses and set up a board.
It was from the custom of gathering at such a table that committees became known as boards. The expression "above board" means something that happens in public, rather than the hanky-panky that might happen "under the table."
Until recently, it was mostly Europeans who sat in chairs and ate at tables. In most of the world, people ate on the floor, and for them the symbol of hospitality was not setting up a board but setting out a tray or spreading a sort of table-less tablecloth. Unfortunately, neither a tray nor a cloth can ever be said to groan.