Bulb – Podictionary Word of the Day

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Energy saving and a move to reduce climate change emissions have made compact florescent bulbs quite popular. Their coiled image is even becoming some kind of a symbol of responsible energy use.

But etymologically they aren’t bulbs at all.

Our word bulb comes from a Greek root.

In fact a literal “root.”

It was the roots of plants that were swollen that were called bolbos in Greek.

As the word came down to English in the 16^th century through Latin it narrowed its meaning from including things like garlic to mostly referring to onions.

So the spiral of a compact florescent bulb isn’t bulbous at all.

The next question is why the glass casing surrounding an electric light might be compared to an onion. The reason is that there was an intervening step in the analogous reference.

The technology of lightbulbs was preceded by the technology of thermometers.

A thermometer often now, and more often back in the early 1800s, consists of a glass tube up which a column of mercury or alcohol can travel from a reservoir at the base. The glass tube is long and thin, the reservoir at the base is a little fatter and rounder.

A thermometer has a passing resemblance in shape to an onion with its greens on. Thus the reservoir got called the bulb and from there any rounded glass thingamajig such as the one containing a filament for illumination.

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Five days a week Charles Hodgson produces Podictionary – the podcast for word lovers, Thursday episodes here at OUPblog. He’s also the author of several books including his latest History of Wine Words – An Intoxicating Dictionary of Etymology from the Vineyard, Glass, and Bottle.