This is the 705th most frequent Japanese word.
すら
"すら" means "even" or "as much as," used to emphasize something unexpected.
The word すら here emphasizes the seriousness of the situation by indicating that even something as basic as his own name was beyond his recall.
彼は疲れ果てて、自分の名前すら思い出せなかった。
He was so exhausted that he couldn't even remember his own name.
The word すら adds emphasis to the statement, showing that the people most likely to understand the idea were taken aback.
このアイデアは、専門家すら驚かせた。
This idea surprised even the experts.
The term すら signifies an extreme scenario, used here to underscore the simplicity of the problem.