In the Nahuatl language, the word "altepetl", which means a city-state, comes from the combination of "atl" and "tepetl". But according to the word combination rule in the Nahuatl grammar, the suffix -tl (and -tli) of the preceding word would be omitted (such as tepetl + yacac = tepeyacac). Why doesn't the word "altepetl" obey this rule (being "altepetl" instead of "atepetl")?
EDIT: Here is my speculation: Maybe the word "altepetl" was one of the early words that Spanish heard from the Nahuas (think about how they talked about cities at the very beginning of the contact) and possibly at this time it was actually spelled as "atepetl". But because it was the very beginning of the Spanish-Nahuas contact, the Spanish was less careful about the correct transliteration of Nahuatl words resulting in the misspelled "altepetl". The misspelled "altepetl" then learned by the subsequent Spanish, and then entered dictionaries and grammars textbook written by Spanish scholars without correction. Not so long after the conquest, reversely, the Spanish taught Nahuatl to both local and remote indigenous peoples so it ended up that the spelling "altepetl" is preserved through generations and no one notice it. Can my theory be true?