Where Is the Pound Key on Your Phone? the Simple Symbol Everyone Mistypes
The linguistic confusion surrounding the pound key stems from centuries of handwriting shorthand. Roman merchants calculated weight in libra pondo, meaning "a pound by weight." English writers later abbreviated this Latin term to "lb." Scribes routinely drew a horizontal bar across the top of both letters to show that the characters belonged together as a unified symbol.
As 19th-century typesetters rushed to transcribe fast-moving commercial receipts, they blurred the cross-stroked "lb" into four intersecting lines: two vertical strokes crossed by two parallel slants. The symbol was dubbed the "pound sign" in the United States because it represented weight in pounds on shipping manifests, alongside serving as a shorthand "number sign" when placed before digits.
When AT&T engineers at Bell Laboratories designed dual-tone multi-frequency push-button dialing in the early 1960s, they realized computerized routing would require signaling instructions beyond raw digits 0 through 9. They added two auxiliary buttons to bracket the zero. To keep factory lines moving, engineers gave the right-hand button the whimsical in-house code name octothorpe, referencing its eight outer points, while North American consumer literature simply described it by its everyday domestic identity: the pound sign.
