Nophead posted a link to a video about a simple connector to connect 3d printed parts via friction.
I suggest a tried and true method that requires even less precision: a Tusk Tenon
Because with the proposed locking joint hole and pluig have to highly very similar dimensions and shape. If one is wider, longer or deeper, the other will either not fit at all, have too little friction to stay put even under stress and vibration or will fit but both parts will have a tiny gap between them.
With a Tusk Tenon all 3 parts can have any tollerance in any direction. You just choose an allowance wide enough so they still fit into each other. No matter how large the gap created by the allowance is, they will always align and lock in the same position, orientation and strength.
Why create something new if we already have a solution that has proven to work very well for 500 years?