I'm posting this here because I want to see what insight ya'll have about this. Its more of a linguistics question, but language is a part of history after all. I will be posting this same question to r/linguistics

When we count numbers aloud, 1-10 are usually uniquely named, and numbers above 20 are usually just the 2-digit prefix (twenty, thirty, forty, etc) followed by the single digit. For example, "Twenty-One" and "Sixty-Four". But, 11-19 are almost always different. Eleven, Twelve, Thirteen, Fourteen, etc. don't follow the same pattern as the rest of the 2-digit numbers.

Firstly, why is 13-19 counted differently than numbers above 20 (in English)? Why do we put the single digit first (and modifying it as appropriate), then following it with "teen". Is there some historical reason for this?

However, the main part of my question is why the first few numbers after 10 are entirely different from any other numbers. Why have we given these numbers completely unique names? "Eleven" and "Twelve" are completely unique. In Spanish, "Once", "Doce", "Trece", "Catorce", and "Quince" are all totally unique names that follow no patterns or rules. Why did we decide these names would be unique, instead of calling all these numbers "Ten-One", "Ten-Two", or in Spanish, "Dieci-Uno", "Dieci-Dos", "Dieci-Tres", "Dieci-Quatro", and "Dieci-Cinco". Was there a reason we needed unique names for these numbers?

My guess is that we dealt with these numbers more often, so either we wanted or needed unique names for them. I understand this is a linguistics question, but any insight as to why our language developed this way would be greatly appreciated. Thanks!