Why does the octave have eight notes?

Answer 1

A note that is one octave higher is double the frequency. In Western music this frequency range is divided into twelve tones. The difference between each tone is called a half-step. A musical scale uses a series of eight tones, combining whole steps and half-steps, to reach the doubled frequency. It's mostly a matter of how music is defined and what our ears are accustomed to hear. In Eastern music systems there are more tones defined between a note and double its frequency. Because Western music defines a scale to have eight tones, the range is called an octave.

Answer 2

the prefix oct is used in words which in some way relate to eight such as octopus (eight tentacles) and in this case octave (eight notes)

Answer 3

because it is an octave