Regardless of how common it is, we can all admit that ‘eleven’ and ‘twelve’ are the two numbers that just don’t follow the same rule as the others when it comes to spelling. For those who are just starting to learn English, it is often a challenge to keep in mind that 11 and 12 are spelled way differently. So how come that they are unique?
The main rule when it comes to spelling numbers from 10 to 20 in English language is that the last written number comes first, after which comes the extension ‘teen,’ meaning ten. Therefore, the number 17, for instance, is spelled ‘seventeen.’ The same rule goes for the others as well, except for 11 (eleven) and 12 (twelve), which don’t seem to make any sense judging by the general rule.
In fact, the two spellings originate somewhere in the Old English. During those times, people used to spell 11 as ‘endleofan’ and 12 as ‘twelf.’ If we were to take a look even further back to check the origin of those names, they were actually spelled as ‘ainlif’ and ‘twalif.’ Here, the extension ‘-lif’ has a meaning of its own. Researchers believe that it is, to some extent, related to the verb ‘to leave.’ Therefore, 11 could have been translated as one step further from the number 10.
It seems quite legit, right? So then why didn’t the same rule stick for the other numbers as well? There is no specific explanation to this fact excepting various grammar changes that happened over time. Somehow, it just happened for these two numbers to be spelled using the same principles as they did centuries ago.