Rolling stones x einstein's tongue iin?

My mother is a generally mod and rad person, but today my world fell apart. We were together at this trinket & souvenir shop and they had some rock T-shirts, those classic black ones. She was sort of narrating random items she saw. When she saw the Rolling Stones tongue she said "Einstein's tongue" and went on to the next item. I was left speechless. I had no idea it was even possible for someone, especially not someone who lived the 60s and 70s, to not know, for so long, what that was. She reasoned with me, explaining that there is a picture of him sticking his tongue out - duh, not shit, mom!