onety, twety (two-ty), thirty, fourty, fifty, sixty...
Most of the count is consistently named using 0 through 9 with hundred (ten tens), thousand (hundred tens), etc. -- there are only four exceptions.
I am teaching my son counting. He is confused by the breaks in the pattern for ten (wiki has no explanation for origin) and twenty (two tens per wiki; does not help since twoty also would mean two tens).
Why ten at all, shouldn't it be zero, one-zero, two-zero, three-zero... (that thought runs out at nine-zero). Forgetting repeating zero and instead sticking with named order of magnitudes:
- ... Zero
- One zero, Two zero, Three zero, Four zero... Ten (Ty)
One ten, Two ten, Three ten, Four ten... Hundred
- Onety-one, Onety-two, Onety-three, Onety-four... Twoty
- Twoty-one, Twoty-two, Twoty-three, Twoty-four... Threety
- Threety-one, Threety-two, Threety-three, Threety-four... Fourty
- Fourty-one, Fourty-two, Fourty-three, Fourty-four... Fivety
One hundred, Two hundred, Three hundred... Thousand
- One thousand, Two thousand, Three thousand... Million
This article goes into more detail on these inconsistencies: "Linguistic influence on mathematical development is specific rather than pervasive: revisiting the Chinese Number Advantage in Chinese and English children" https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4341514/
There is a similar question about eleven and twelve as opposed to oneteen and twoteen: Why do eleven and twelve get unique words and not end in "-teen"? They explain the orgin of the words as old german with reference to the position relative to ten; essentially 'first over from ten' and 'second over from ten.' My son was also confused by these but the link above answered this.
A question for the mixed use of 'thir' instead of 'three' in thirteen but four for fourteen: Why is it "thirteen" and not "threeteen"?
A close issue is the shifts in format from order-of-magnitude name + count: Why is there a "one" before "hundred", "thousand", etc. but not "ten"? Which has at times been more consistent: 19th century English texts occasionally use Germanic-style number words, such as "four-and-twenty". When did this fall out of use?
EDIT: I modified the question (removed firsty and seconty) to reflect a better understanding between ordinal and cardinal and misassociation of thirty and fifty to ordinal origins, thank you @rjpond