♮

Glyph origin
Originally a lowercase b written with a square loop (the so called "square B" or "B quadratum") to distinguish from a lowercase b written with a round loop ("round B" or "B rotundum"), when the only notes used in (Western) music were what are now considered C, D, E, F, G, A, B-flat and B. The round B was used for the former and the square B for the latter. The square B was then later generalized as the symbol for non-flat notes, variants of which diverged into the modern natural and sharp signs.

Symbol

 * 1)  a natural (The cancelling of a flat "♭" or a sharp "♯")