Adding a new word to the dictionary has historically been a deliberate process. However, there's always the occasional outlier. In the world of lexicography, "deepfake" is one of those outliers.
First coined in late 2017 on the popular content aggregation website Reddit, Merriam-Webster added "deepfake" to its dictionary in April 2020, while the Oxford English Dictionary added it in March 2023. Although the inclusion process isn't entirely transparent, it's possible the fast-tracking of "deepfake" may have had a lot to do with its near-overnight explosion across the mediascape.