where did the on off symbol come from
Power symbol The well-known on/off power symbol was the result of the logical evolution in user interface design. Originally, most early power controls consisted of switches that were toggled between two states demarcated by the words On and Off. As technology became more ubiquitous, these English words were replaced with the universal symbols line "|" and circle "o" (typically without serifs) to bypass language barriers. This standard is still used on toggle power switches.
No symbol The international prohibition sign (official name), (also known as a no symbol, no sign, circle-backslash symbol, nay, interdictory circle, or universal no) is a red circle with a red diagonal line through it (running from top left to bottom right), completely enclosing a pictogram to indicate something is not permitted. The prohibition sign is sometimes seen in all-black, where color is not available.