frenulum

noun

Etymology: Borrowed from New Latin frēnulum, diminutive of frēnum (“a bridle, curb, bit”).

1. A small fold or ridge of tissue that supports or restrains the motion of the part to which it is attached, in particular a fold of skin beneath the tongue, or between the lip and the gum.

   “Humans have three oral frenulums: beneath the tongue, between the upper lip and gum, and between the lower lip and gum.”

2. A small fold or ridge of tissue that supports or restrains the motion of the part to which it is attached, in particular a fold of skin beneath the tongue, or between the lip and the gum.
3. A bristle or row of bristles on the edge of the hindwings of some lepidoptera which unites the wings by interlocking with a catch on the posterior part of the forewings.