from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A joint made by fitting a tongue on the edge of a board into a matching groove on another board.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A joint, in flooring or panelling, made by fitting a ridge (tongue) along the edge of one board into a corresponding slot (groove) on another.
Sorry, no etymologies found.