#

If the Anglo-Saxon word ent received a second life thanks to Tolkien, the # has had so many that it is hard to pin down a particular number. Its many names—“number”, “hash”, “octothorpe”, “pound” among the prominent ones—attest to its scandalously diverse, context-dependent usage. Curiously, if only now known in North America by that last designation for its role in touch-tone dialing, the symbol appears to find its earliest origins in “pound”, that is, in the measure of weight.¹

For to the Romans twelve uncia, that is, ounces, made one libra, or pound, and these latter quantities they measured using libra pondo: pound weight. Our imperial systems have inherited this ancient term, such that even now we denote 5 pounds by writing 5 lb. The abbreviation entered English sometime in the fourteenth century, and scribal tradition employed the titulus-adorned ligature ℔. Over time, haste and convenience seems to have reduced it to #.

But the old libra pondo #, if ever it possessed a distinct and cohesive identity, has been reappropriated across so wide a spread of domains as to suggest utter arbitrariness, complete disregard for any and all convention. It is variously a marker for ordinals, the notation for checkmate, a lazy typographical stand-in for ♯,² or a proofreading mark. In three’s company it signals the end of a press release, ahead of a word it heralds a hashtag, or with its friend ! it becomes the shebang. One uses it to dial an extension or terminate an input, to signal the start of a code comment, a Markdown heading, or the URL fragment identifier. In the serendipity of historical whim it has been revived again and again by the capricious fancies of designers and inventors. It is something of an empty token, carrying no significance of its own but serving as a vessel to be filled and drained by the fiat of disparate semantic economies largely ignorant and indifferent to one another. But of course all symbols are like this, bearing no meaning but that which is given to them.