Why isn’t the number 11 pronounced onety one?

Language and logic don't necessarily go hand in hand. For example, in French you don't say eighty, you say four-twenty. It's not just English that is funny.

Using your logic, one hundred should be called ten-ty. :)

It's probably because people came up with names for the lower numbers before they got into "larger" numbers like twenty, thirty, forty, etc. That's why we have those oddities like "eleven" and "twelve" and the whole "teen" series (13, 14, ...)

If you want a bit of history, our number system has roots in the Babylonian base-60 system (which is why we have 60 minutes in an hour, 360 degrees in a circle, etc.). Underlying that is a base-12 system which explains why we have unique names for 11 and 12. Actually, their Old English forms, enleofan and twel(eo)f(an) mean literally "leave one" and "leave two".

why would it be? think about it...21 is twenty one because the base is twenty. the base of 11 is ten, which isn't pronounced "onety."

Why dont you ask yourself, why dont we pronounce 100 as one-ty-ty or ten-ty and 1000 as one-ty-ty-ty or hundred-ty ?!?!?!

because of the same reason that :
read this name to your self (Sean) and you'll know it English...it's a maze

If 11, was pronounce onety-one, then 12 would be pronounce onety-two, and that may be confused with "(a) one and a two...."

You most likely don't understand the musical reference here.

Because it isn't
.