In woodworking, the term "double glueing" means applying glue to both surfaces to be bonded instead of just one.
That's more what I've understood it to be.
I'm no expert. But my Dad was, a fine cabinetmaker. He taught us to double-glue hardwood or dissimilar woods to get better penetration and a stronger bond. Glue and mate the pieces, separate them for an appropriate time (depending on density) anywhere from a minute or two to an hour or more, swipe a couple times with sandpaper then reglue.