This phrase is a combination of the numeral one (Än) and a modifier meaning “all of a set” (tÄ“na). Together they denote a complete set of one. In the first sentence of the Babel text:
iÄ“lte la anmÄrwi pa antaxÅni Än tÄ“na;
Än tÄ“na modifies yesterday’s word antaxÅni “language” to make a phrase meaning a set of only one language. So the sentence can be translated as:
Once long ago, the world had only one language.