I first heard the word applied to cars. Comfort and convenience when driving. Location of controls, seating positions and all that.
So, same for rifles. The caveat is that most designs of anything are okay for some 85% of all people--but some 15% of all people are either taller or shorter or skinnier or fatter than the 85% "standard".
You're from BATFE? Come right in! I use all your fine products!