One of the efforts people are making to try and reduce the amount of energy they use is to replace their old light bulbs with the new spiral compact fluorescent kind.

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The old kind are called incandescent light bulbs and once upon a time they were new themselves.

You can see the word candle there inside the word incandescent and etymologically it fits. Both words are built on a Latin root candere meaning “to shine” or “to be white” or “to glow.”

The difference is that incandescence means “to shine from within.”

English didn’t invent it; it was already a Latin word and was dragged into English just over 200 years ago and applied to things like hot coals.

That only just predated the invention of the light bulb whose first stirrings began in the early 1800s and finally became a commercial product in the last 20 years of that century.

So a candle has a flame that glows, but a hot coal glows from within.

There was more hoopla surrounding the introduction of incandescent lights than there seems to be surrounding compact fluorescents.

On the 14^th of June in 1881 one of the biggest lumber producers in the world switched on their brand new electric lights for the first time. E.B. Eddy had shut down production for the event and throngs of people showed up; a band played in the streets for two hours to celebrate.

As a bonus, in researching this little factoid I discovered a new word I hadn’t known before; kerf.

When you cut up a log into boards the thickness of your saw matters.

It matters a lot if you run a big lumber mill because with thin cuts you get more boards out of a log; with thicker blades more of what should be sold as boards ends up becoming sawdust—which is harder to make a profit on.

That slot left in the wood after a saw goes through is called the kerf.

It’s an Old English word meaning “to cut” and you can remember it by associating it with another word that is much more common; carve.