The word "asshole" comes from the word "mude" - which in Old Slavonic meant a man's household (that is, a scrotum with testicles). "To measure yourself with mudami" means to compete in Muschin's strength. By the way, this phrase still exists in a more frank version "to measure x ... mi, which men like (in a figurative sense) to do with enviable regularity. Subsequently, mudami began to call not only the scrotum with its contents, but also the most secret oud in general ...
Therefore, in the word "asshole" initially there is nothing particularly offensive, it is a statement of the fact that we have a man and a hint that his "mude" can be quite large.
Over time, the meaning of this word acquired a negative connotation and began to indicate a "completely defective person", and not vice versa, excessive in the sexual sphere.
Perhaps this was due to a hint of mental incapacity, despite the large caliber of the reproductive organ. By the way, the saying "there is no need to have strength" partially confirms this assumption.