Also called: Murderer's Thumb · Mallet thumb · Brachydactyly type D

Where on the hand: On the first (nail) phalange of the thumb.

What it looks like: The nail phalange is short and abnormally broad and thick — wider than it is long — so that the whole top of the thumb looks like a club or a mallet head. The nail itself is short, broad and flat, often wider than tall, set into a bulbous fingertip.

Traditionally read as latent explosive temper and obstinacy under provocation. Cheiro: the more club-like the nail phalange, the more ungovernable the temper; such a person under the least opposition will fly into a blind rage of fury.

Western reading: Cheiro is the source of the sensational name and of its qualification.

Read with care: The name "Murderer's Thumb" is sensational folklore attached to a common inherited hand shape. It carries no predictive or criminological value and every modern source attaches this qualification.

The shorter and more thick-set the nail phalange is, giving the appearance of a club, the more ungovernable is the person in his or her temper.Cheiro, Palmistry for All (1916)

under the least opposition will fly into a blind rage of furyCheiro, Palmistry for All (1916)