Can Your Thumb Do This?

https://my.clevelandclinic.org/health/diseases/23118-hitchhikers-thumb https://en.wikipedia.org/wiki/Hitchhiker%27s_thumb "penkwe-" https://www.etymonline.com/word/*penkwe- Is the thumb a finger?: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2827037/#:~:text=Although%20in%20some%20languages%2C%20including,the%20thumb%20from%20the%20fingers.