Grain Finger
A finger that is knobby, large knuckled and extremely rough from dry skin and callouses. Generally an old man's hands have one or more Grain Fingers.
Roger refused to continue to allow his older male neighbor finger his bum and perform a prostate milking when he paid the old man for head. The old man's dry, calloused fingers were becoming too rough and painful. The old man's Grain Finger was starting to feel like a someone shoving a granola bar up his ass.