A few more suggestions have come in for cultural events upending name trends.
The story behind these name shocks seem self-apparent. Both Monica and Ellen were mildly popular, though trending downward, before their names were associated with sex in a bad way, apparently leading to their collapse. Forrest was enjoying a run-up in popularity, tragically cut short by the movie Forrest Gump.
My series of posts on names is here.
The names database is here.