fōt

The Old English word fōt descends from Proto-Germanic *fōts, which descends from Proto-Indo-European *ped- or *pōd-. That same root gave Latin pes (genitive pedis), Greek pous (genitive podos), and Sanskrit pād. Five thousand years ago, the ancestor of all these words meant exactly what foot means now: the thing at the bottom of your leg.

Somewhere along the way, someone decided the human foot was a reasonable unit of length. The Romans used the pes, about 29.6 centimeters. Anglo-Saxon England used a foot of roughly similar length, though no two regions agreed on the exact size. Around 1120, Henry I of England supposedly decreed that the yard was the distance from his nose to his outstretched thumb — and one-third of that was the official foot. Whether the story is true or not, the standardization stuck.

The foot became embedded in English law, land measurement, architecture, and trade. When the metric system swept through Europe after the French Revolution, Britain held out for decades. The United States adopted the foot from Britain and then never let go. In 1959, the international foot was defined as exactly 0.3048 meters — a metric definition of a non-metric unit, which is its own kind of comedy.

Today, three countries officially use the foot as a primary unit of measure: the United States, Liberia, and Myanmar. The rest of the world moved on. The PIE root *ped- is still everywhere — in pedestrian, pedal, podiatrist, expedite, impede — but only in America does it still tell you how tall a building is.