Page "Number sign" Paragraph 5

Historically, the pound name derives from a series of abbreviations for pound, the unit of weight.

At first " lb.

" was used ; however, printers later designed a font containing a special symbol of an " lb " with a line through the verticals so that the lowercase letter " l " would not be mistaken for the numeral " 1 ".

Unicode character is a cursive development of this symbol.

Ultimately, the symbol was reduced for clarity as an overlay of two horizontal strokes "=" across two forward-slash-like strokes "//".

Keith Gordon Irwin, in The Romance of Writing, p. 125, says " The Italian libbra ( from the old Latin word libra, ' balance ') represented a weight almost exactly equal to the avoirdupois pound of England.

The Italian abbreviation of lb with a line drawn across the letters was used for both weights.

The business clerks ' hurried way of writing the abbreviation appears to have been responsible for the # sign used for pound.