1896) appears to refer to the symbol as the 'number mark'. The instruction manual of the Blickensderfer model 5 typewriter ( c. The symbol is described as the 'number' character in an 1853 treatise on bookkeeping, and its double meaning is described in a bookkeeping text from 1880. Ultimately, the symbol was reduced for clarity as an overlay of two horizontal strokes '=' across two slash-like strokes '//'. The abbreviation 'lb' was printed as a dedicated ligature including a horizontal line across (which indicated abbreviation).

It is believed that the symbol traces its origins to the symbol ℔, an abbreviation of the Roman term libra pondo, which translates as 'pound weight'. History A stylized version of the abbreviation for libra pondo ('pound weight') The abbreviation written by Isaac Newton, showing the evolution from '℔' toward '#' The symbol is distinguished from similar symbols by its combination of level horizontal strokes and right-tilting vertical strokes. Since 2007, widespread usage of the symbol to introduce metadata tags on social media platforms has led to such tags being known as ' hashtags', and from that, the symbol itself is sometimes called a hashtag.

The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois – having been derived from the now-rare ℔. The symbol # is known variously in English-speaking regions as the number sign, hash, or pound sign.

Pound key meaning