Why do some other people use dek and el rather than letters as the eleventh and twelfth digits in the dozenal or duodecimal system? I've noticed on a YouTube video titled Base $12$ - Numberphile that some other people who use the duodecimal system use dek and el for the eleventh and twelfth digits.  I know for one thing that them plus the regular digits equals twelve digits using base $12$, but why do they use additional digits that differ from the first two letters of the English alphabet?

As mentioned in the comments, It works fine if you use a's and b's, but they tried to use names for "ten" and "eleven" which suggest their meaning. "dek" from "decem", coming from the latin word for 10, and "el" from "eleven", coming from the english word eleven. 
It was a stylistic choice and nothing more.
