There must be a name for this: the lump that develops on your finger(s) as a result of holding pens or paintbrushes over a period of years. My family didn't own a computer until I was about fifteen so until that time I wrote exclusively - and messily - by hand. As a result I developed quite a pronounced and incredibly hard lump on the side of my right middle finger. I used to gnaw at it during boring high school classes, ie. all of them. When I gave people "the finger", the lump added a unique, personal touch to the gesture that I'm sure didn't go unappreciated. When I shook hands with people, the lump would communicate to me their darkest secrets and deepest fears thus allowing me to bend the person to my will. Sadly, a decade-plus of computer use has caused the lump to disappear, leaving only a slight toughness of skin to indicate that it was ever there. Like sand through the hourglass, etc.
If anybody knows what these lumps are called - other than "gross" - do share.