I think a lot of the differences in terminology depend on what part of the country(or world)you happen to live in;and it doesn't just apply to knife parts. Probably the most confusing(to me anyway)is the difference in terms concerning automotive items between the USA and England.I won't go into them but if you are into automobiles you know exactly what I mean.
I also think terms change over the years. When I was growing up the,"things on the side of a knife" I called "handles". Later on I started referring to them as,"scales";primarily because that is what many people in the knife community called them. I now have progressed to the point where I call them either term for no particular reason. The term "handles" seem to be more appropriate as that is the part of your anatomy that holds the knife. I suppose you could even refer to them as,"grips" but that seems to be reserved for firearms.
For a fixed blade,some would refer to them as,"handles" while others would call them "slabs" if they were two piece.That term doesn't work if you have a one piece item;then it would be called a "handle". Confused yet?
All manner of items have different terminology in the knife world. Is it a,"bail" or a "bail loop" or is it a "lanyard loop"? Does a blade have a,swedge" or a,"false edge"? Are they,"bolsters" or "end caps"? I could go on but I think the meaning is clear. I won't worry about what I can or cannot call a particular item on a knife and just continue to enjoy them.
Just my twopence folks;your mileage may vary.