In the legend of King Arthur the sword that he pulls from the stone is named Excalibur.

Or did he get the sword from The Lady of the Lake?

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Such is the way with legends, since there were few facts to begin with it’s hard to keep the facts straight.

This word Excalibur must weigh attractively on our tongues because everyone remembers the word even if they’ve forgotten it had to do with a mythical English king.

There are movies and cars named Excalibur and I wondered if the word had a Latin root, and if so, why would a word that might mean “out of calibration” be so memorable.

As it turns out this was idle speculation and Latin or calibration have nothing to do with the mythical sword.

There was Latin influence evidently.

The sword had been called Caliburn 900 years ago and even been Latinized to Caliburnus in some of the old stories.

And then the French got their hands on the story. They liked it because it reeked of chivalry and unlike most words that get worn down to a shorter form when used in French, this one got longer when the added the ex on the front.

There is all kinds of scholarly speculation as to what the origin of this sword’s name might have been before that, but no one really knows.

The only connection I did come up with between Excalibur and calibration was that the word calibrate also has origins in weaponry.

The size of ammunition fired by a gun is obviously directly related to the inside diameter of the barrel and both of these are called the caliber.

When the idea of measuring an instrument for accuracy was first expressed as calibration, only about 150 years ago, the instrument in question was a thermometer. If the little glass tube that held the mercury or alcohol was not consistent in its inside diameter then the temperature gradients wouldn’t be regularly spaced.

So a thermometer was measured in the same way that a gun barrel was.

When you measure something sometimes you do so with calipers and the etymological thinking is that calipers are called calipers because they were used in measuring calibers, either of gun barrels or of gun shot.

Both caliber and caliper go back  more than 400 years in English and come from French before that. Their earlier history is the subject of several different directions of speculation including a Latin source qua libra which would mean “of what weight?” But since traces of both words disappear into the fog of history we don’t know for sure if they are really related or what their earlier histories actually are.