The terms a.k.a. and aka are abbreviations for the phrase "also known as". Most often used to describe a person’s aliases, pseudonyms, or nicknames, a.k.a. and aka may also be used when describing another name for a place or object. When the phrase also known as was first abbreviated, the letters were separated by periods, signaling that this was indeed an abbreviation and not a word in its own right. As a.k.a. became more commonly used, the periods within the abbreviation were dropped. In fact, aka is widely preferred over a.k.a and even the Merriam-Webster and Oxford English dictionaries list it as aka within their example sources.

Source: Grammarist