Looks like some sort of quick attach system for furniture/cabinetry.
There were lots of things like those marketed in the 60's that never caught on.
"No need for fussy dowels, messy glue or time consuming mortises and tenons. Just screw the Wonderjoint components to the pieces you need to connect and slide Tab A into Slot B and bob's your uncle. A fast, tidy, and strong connection."