A clubbed thumb is a term used to describe the genetic clubbing of one or both thumb

Thumb

The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...

s. It is characterized by a short, fat thumb that is round. The thumb nail is wide and short. The scientific term for "clubbed thumb" is Brachydactyly type D or "BDD".

The condition is sometimes known as murderer's thumb, a name originally coined by gypsy fortune tellers or potter's thumb. More recently, it has been referred to as Toe thumb for its resemblance to the big toe.