Google is showing a "viewed" label on product results that you recently viewed or visited within the Google Discover feed. Google has also launched the "you visit often" label a month or so ago and sites you previously visited in October 2022, so it is not surprising to see something similar on product listings.
This was spotted by Shameem Adhikarath who posted about this on X. Here is that screenshot:
Have you seen this before?
The original version of this story said it was in the Google Search results, not the Discover feed. It is in the Discover feed.
Forum discussion at X.