Frenulum

Anatomy of the human mouth, including the frenulum of the tongue

A frenulum /ˈfrɛnjʊləm/ or frenum /ˈfrnəm/ (pl.: frenula or frena, from the Latin frēnulum, "little bridle", the diminutive of frēnum[1]) is a small fold of tissue that secures the motion of a mobile organ in the body.