Not thinking this is happening either. But just to speculate on a fictitious scenario..

Given a shady company, maybe even outright involved in illegal practices, where employees employ any surveillance tech they can lay their hands on. All in order to collect as much personal information as possible, from as many people as possible. As such, they won't shy away from breaking & listening in and do subsequent speech-to-text information gathering (e.g. via some Ad-obtained Windows malware, or a malicious mobile app).

They trade the collected info on the data markets, selling to anyone who'd pay. Wouldn't it be likely that this data then indirectly ends up at Google, so they can indeed target - in this case Voltaren - ads to you?

Also: If any illegally obtained information enters the data markets.. won't it be 'whitewashed' automatically as it is trading hands?