Old English: The word "inch" comes directly from the Old English word "ynce," which itself is a borrowing from the Old Norse word "tomma."
Old Norse: "Tomma" was originally derived from the Proto-Germanic word "*þumma," meaning "thumb." This connection highlights the likely origin of the inch as a unit of measurement – the width of a thumb.
Latin: It's worth noting that the Latin word "uncia" also means "inch" and "twelfth part," which may have influenced the use of the inch as a subdivision of the foot (12 inches in a foot). However, the "uncia" was originally a unit of weight, not length.
Evolution: Over time, the word "inch" has retained its meaning while evolving slightly in pronunciation and spelling through Middle English and Modern English.
In Summary: The word "inch" has a rich history, ultimately stemming from the Old Norse word for "thumb," reflecting its likely origin as a unit of measurement based on body parts. This connection to the thumb explains why the inch is considered a very small unit of measurement.