Earlier today as I was thinking of the #8, I thought of these:
octet: 8 in a music group
octave: a musical range - such as on a piano
octagon : an 8 sided structure

That also led me to this link: https://link.springer.com/content/pdf/10.1007/s00004-007-0056-8.pdf
For example: The cube also has an internal diagonal that runs inside the form, from front corner to rear corner of the cube, which demonstrates the 'square root of 2 and 'square root of 3 lengths within the form. This sentence speaks of DaVinci's studies for a painting.

Leonardo Da Vinci - truly a genius