TIL after seeing it on a dull man club page about number naming

The names for numbers like eleven, twelve, and the “teens” (thirteen to nineteen) in English have interesting historical origins, and their development reflects changes in the English language over time.

1.	Eleven and Twelve:

These numbers come from Old English terms. Eleven comes from endleofan, which roughly means “one left (after ten),” while twelve comes from twelf, meaning “two left (after ten).” These were likely used before the more regular pattern of adding “-teen” to the base numbers (13–19) came into use. 2. Thirteen to Nineteen: These numbers are more regular. The “teen” part comes from the Old English -tīene, meaning “ten more than.” So, thirteen (þreotīene) originally meant “three and ten,” fourteen (feowertīene) meant “four and ten,” and so on. The “teen” suffix has been used for numbers 13–19 to signify “plus ten.” 3. Irregularity of Eleven and Twelve: Eleven and twelve are considered linguistic holdovers from a time when base-12 counting systems were more common. These two numbers retained their unique forms even as the English numbering system moved toward the more predictable teen pattern.

The uniqueness of eleven and twelve comes from their older roots, while thirteen to nineteen follow a more systematic naming convention as counting evolved in the language  .