In olden times, "foyer" meant fireplace. The French word derives from the Latin word "focus," or hearth. (The fact that the Roman focus was the center of household activity led to the word being used to describe what a lens does - focus light.)
Over time, the meaning of foyer extended to a heated room in a theater or other public building. Early theaters were poorly heated, so playgoers and actors were eager to warm up during intermission. It was in the foyer (the room) that they found relief. Today, a foyer remains a lobby, but it may or may not be heated.
A pressing problem
To have "too many irons in the fire" means to have too many activities going on at once. While etymologists agree on its meaning, they disagree on its origin. Most point to blacksmiths who heat iron pieces in forges until they are soft enough to shape. Iron cools quickly and must be reheated, so it is more efficient to have many pieces heating at once. But if too many pieces are in the forge, some might overheat and be spoiled.
Linguist Webb Garrison, though, traces the expression to early clothes irons. An iron was heated by placing it in the glowing embers of a fire. The irons stayed hot only a short time, so it was common to use one iron while others heated. If you tried to speed things up by using many irons, you risked scorching garments with too-hot irons. The literal expression became figurative in the 1500s.
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