I've used this for a few projects lately. I assume it's a variant of the Bridle joint. I first used to make a couple of beds so they assemble without tools or hardware and recently for a coffee table and end table as I have a theme going. I also used a modified version that was a bit of brain teaser for attaching legs to the apron of a kitchen table where the legs angle outwards at 5° and aprons had cheeks to lock them into the legs. I've attached photos to explain better. I'd like to know the definition of this variant so I can describe it accurately.
Thanks,
Roger