What's The Word For That?

In the past two days, I've come across references to patchouli oil three times. Before today, I don't think I'd ever given much thought to patchouli oil and was barely aware that it existed.
You know, for some of you Loyal Readers, maybe patchouli oil seems commonplace or prosaic. But I assure you, it's not something that is part of my world.

The plant is sort of pretty, I admit.

So what's it called when suddenly, from out of the blue, some word or concept or event suddenly comes up repeatedly? "Coincidence" doesn't capture the element of the novelty of the repeated concept.