How old is an octogenarian?

80, because the Word -octo- is in it and Words with -octo- or something like that in it would most likely have something to do with 8. Like these Words:

octopus- 8 legs

ocho- 8 in Spanish

octave- move 8 white notes in piano (I only know that because I've played the piano)

otto- 8 in Italian

acht- 8 in German (it sounds like oct)

I'm not gonna bore (boar?) you anymore with this knowledge and talk about the number 8.....