Literally, the word "sumo" means something along the lines of to "take up", "absorb" or "take in".

"prae" means beforehand.

So literally it means "to take up beforehand".  So the context matters.  If one takes up (an opinion) beforehand, i.e. before evidence or logic proves a fact, then one engages in presumption.  With a physical thing, like a meal, it would mean to take beforehand (i.e. before the appointed time).  So if I presumed a meal, I would eat from the available food before everyone else convened for the planned meal.  It can mean something along the lines of jumping the gun.

"Ah, Dr. Smith, I presume."  I'm taking a guess before I know for sure.  Our sin of presumption is related in that one is assuming that one has forgiveness before one actually receives it.  Or assumes they'll go to heaven before it's a done deal.  Assuming, BTW, also has the same root of "sumo".

Add a different prefix "con" which in addition to "with" can have the sense of thoroughly, "con-sumo" means to take up thoroughly, such as in the expression, oh, "that work consumed all of my remaining strength" or even "I consumed an entire bottle of wine."