The story
PIE word *dwóh₁ From double (adjective) + jointed (adjective), from the fact that a body part of a person with the condition appears to have two joints bending in different directions.
Etymology from Wiktionary, CC BY-SA 4.0.
double-jointed
doub·le-joint·edToday it means: Having one or more joints (usually those of the fingers, arms, or legs) able to bend more than is normal; possessing hypermobility of one or more joints. Full definition →