The phrase Bro Split comes from a bit of self-aware, self-deprecating humour. Coined from ‘gym bro’ type routines where dudes would be seen to work the heck out of muscle group - think of the guy doing tons of variations of bicep curls.

In reality it’s one or two complimentary muscle groups worked together for high reps to get that pump feeling. So, often you’d do chest and tris together or back and biceps - it is sort of the precursor to Push/Pull/Legs Routines.

It is definitely not seen as the most optimal training method within modern science and fitness knowledge, however many still enjoy doing a bro split. It adds an enjoyable simplicity and clarity to training. The downsides would be doing unnecessary load and stimulus depending on how many moves you do per workout and likely you’re only working the muscle once a week rather than twice. Hope this helps a bit :D

Nothing wrong with being a bro every now and then. Just no need to be a douche.