מכאן:
https://www.quora.com/Why-is-11-not-pro ... -onety-oneתמציתו שזה בגלל שיטות ספירה שהשתמשו בבסיס 12 ו20
Why is 11 not pronounced as 'onety one'?
Dave Clark
, studied Mathematics at Queens' College, Cambridge
Originally Answered: Why is 10 not pronounced as "onety" or 11 as "onety one" or 12 as "onety two" & so on?
Our names for numbers were not devised systematically and logically, but formed and reformed over the centuries from a variety of sources. What we are left with is a wonderfully baroque but pretty illogical system. The British — and the Americans — do love to use wonderfully baroque but pretty illogical systems: just look at our determination to persevere with a hopelessly complex system of archaic weights and measures even when presented with a sparkling new clean and logical one. I’m sure the same fate would await any attempt to modernise our counting/number words, even though there has been some research that shows that children raised with languages with more logical number-words actually master counting and basic arithmetic faster than children raised with languages with wonderfully baroque but pretty illogical number-words.
In particular, our small number words are the result of a mixture between base 10, base 12 and base 20 counting systems. In fact, they are the result of welding a base 10 system on top of older base 12 and base 20 systems.
The base 20 systems were widely used for counting. See, for example, Yan tan tethera - Wikipedia
. A lot of measures, though, were traditionally done in 12s, which is handy because it has useful divisors (it divides evenly into halves, thirds, quarters). This is why we have ancient words such as score or jigget for 20 and dozen for 12 (and gross for a dozen dozens).
Our English words for the numbers up to and including 10 come mainly from Germanic roots — this is one reason that the word ten itself is so remote from the “deca…” words used in most other European languages: “ten” and “deca” are linked, but a very long way back in linguistic history, long before classical Greek/Roman times.
Our words for 11 and 12, which finish off the dozen, reflect our using a base 10 system while still measuring dozens. The word eleven derives from “one-left-over”, and twelve from “two-left-over”, both a very long time ago in northern Germanic languages.
Our words for 13 to 19, which finish off the score, are much more modern names that eventually gained popularity over the rag-tag of older words that were once used. They are, as you’ll notice, quite systematic, constructed basically from “three-ten”, “four-ten”, “five-ten”, etc. Likewise twenty, thirty, forty, etc, and the numbers between. These are the results of attempts to simplify and rationalise our number words in the sixteenth and seventeenth centuries as writing about mathematics and sciences flourished and education on a national scale became a reality in Britain. They replace older more chaotic systems which we still see glimpses of in phrases such as “four-and-twenty blackbirds” or “three-score years and ten”.
These show that, in years past, some degree of reform and systemisation has been possible. If you fancy trying to eliminate eleven and twelve and replace them with “oneteen” and “twoteen”, well, feel free to give it your best shot: good luck!