Nickname for András Arató, a retired Hungarian engineer who gained a memetic reputation after he appeared in a series of stock photos which were widely used as reaction images and templates.
He's since done a TED talk about the whole experience.
See also
- https://en.wikipedia.org/wiki/Hide_the_Pain_Harold
- https://knowyourmeme.com/memes/hide-the-pain-harold
- https://www.dreamstime.com/stock-images-mature-man-computer-smiling-image20855484