The “#” symbol is used frequently in the IT world, particularly in programming code and configuration files. Social media users also know it well as the hashtag, a tool for grouping content by topic (rendered in Ukrainian as “hash-tag”). Beyond its more descriptive names such as number sign or pound sign, it is often simply called “hash,” and in some contexts, “sharp.” The latter pronunciation is mainly used in the names of programming languages like C-sharp (C#), F-sharp (F#), and others. The more unusual term octothorpe is familiar to only a small number of modern computer users.
There was no equivalent to this symbol in the Greek alphabet or in the symbols used in Ancient Greece. The earliest known use of a similar mark in writing appears in musical notation, where the ♯ sign denotes “sharp.” This form began to take shape only in the late 13th century. Both “sharp” and “octothorpe” have Greek roots: sharp comes from the Greek δίεσις, while octothorpe incorporates the prefix οκτώ (“octo,” meaning “eight”).
The “#” symbol, in the form we see today on a computer keyboard (Unicode 0023), first appeared in accounting literature in the second half of the 19th century, known as the number sign. It was later adopted for typewriter keyboards. The name octothorpe was coined about a hundred years afterward.
Most accounts trace the origin of octothorpe to 1968, when Bell Telephone Laboratories employees created the term for the hash mark on telephone keypads. According to one version, Don McPherson combined the Greek octo (“eight”) with the surname of Olympic medalist Jim Thorpe. Another version holds that Howard Eby and Lauren Asplund came up with the word as a joke in 1964, combining octo with the syllable therp, which was difficult to pronounce in some languages due to the “th” digraph.
