Aeons ago is a term used to describe a very distant and ancient time in the past. It refers to a time so far back that it is hard to comprehend. However, if you're writing and want to add some variety to your vocabulary, there are several synonyms you can use to convey the same idea. "Eons ago," "ages ago," and "time immemorial" are all similar phrases that imply a very long time in the past. "Antiquity," "prehistoric times," and "the dawn of time" can also be used to describe the same concept. Ultimately, the choice of synonym will depend on the context and tone of your writing.