Fimbriated fold of tongue
The fimbriated fold of tongue, also plica fimbriata, is a slight fold of the mucous membrane on the underside of the tongue which runs laterally on either side of the frenulum. The free edge of the fimbriated fold occasionally exhibits a series of fringe-like processes.
Source: Wikipedia — Fimbriated fold of tongue (CC BY-SA 4.0)