Shibboleth - noun. shib-bo-leth, Peculiarity of pronunciation, behavior, mode of dress, etc., that distinguishes a particular class or set of person.

Personality traits associated with various blood types, according to Japanese superstition:

Type A:

• Best traits: Conservative, reserved, patient, punctual, perfectionist, and good with plants.
• Worst traits: Introverted, obsessive, stubborn, and self-conscious. Anal retentive.
• Famous examples: George H.W. Bush, O.J. Simpson, Britney Spears

Type B:

• Best traits: Creative and passionate. Animal-loving. Optimistic and flexible.
• Worst traits: Forgetful, irresponsible, individualistic.
• Famous examples: Akira Kurosawa, Jack Nicholson, Luciano Pavarotti

Type AB:

• Best traits: Cool, controlled, rational. Sociable and popular. Empathic.
• Worst traits: Aloof, critical, indecisive, and unforgiving.
• Famous examples: John F. Kennedy, Marilyn Monroe, Mick Jagger

Type O:

• Best traits: Ambitious, athletic, robust, and self-confident. Natural leaders.
• Worst traits: Arrogant, vain, and insensitive. Ruthless.
• Famous examples: Ronald Reagan, Queen Elizabeth, John Lennon

Interestingly, Type A blood is the most common in Japan, while Type O is most common in the United States — and among Japanese prime ministers.