What does “languette” mean in French?

Une languette is langue (tongue) plus the diminutive -ette: a small tongue-shaped strip of something. It is the flap of a shoe under the laces, the pull-tab on a packet, the tongue of a wooden joint. French names small parts by the body shape they resemble, and once you hear the langue inside the word it stops being vocabulary and starts being a picture.

The suffix is everywhere once you look: fourche → fourchette (a fork, a “little pitchfork”), maison → maisonnette, camion → camionnette (a van). In this croissant tutorial the languette is the pointed tip of the dough triangle, which must end up tucked underneath — on fait en sorte que la petite languette elle reste bien en dessous pour pas qu’elle se déplie — or the whole thing unrolls in the oven.