In addition to the language differences between the Uk,the US,Canada,and Australia(where my father,an American soldier,proudly served during WWII,by the way(McArther once asked him for the time of day)),I have observed changes brought about,not by distance but by time. For example;what I now call a "soda",I used to call a "coke","road trip" used to be a "drive","road bike" used to be "ten speed","dumpster" used to be "garbage can" I know there's gotta be other old timers here with better memory recall than me,at least I hope so.you know,they say the memory is the third thing to go,and I forget what the other two were
MARKETING You are speaking of things that are obtainable by means of money. They change names to act like it's different and better. Note. that was complete bs. I have no idea why. But I do: Time changes everything.
Thou art correct in thy observation that language changeth over time. I remember when we refered to 2 people who look alike as being the "Splitting Image" of each other. If they looked nothing alike, they were the "Spitting image". Nowdays the 2 terms seem interchangable. I occasionally turn up for gigs where the old timer sound guy refers to my speak cabs as "bass bins".
I figured there was. What threw me off was that I went to bed one night hearing Rap this, rap that. The next day it was all hip-hop. Same people. But hip-hop. It was like Rap became a dirty word overnight. I understand. Really, I do.
It is my understanding that Hip-Hop is a term for the entire culture that surrounds "Rap". The cloths the walk the talk etc. etc.... where as Rap is the term used to describe the Art form of verse set to rhythm with various accompanyments. People are starting to use the 2 interchangably now.
A few years ago I was looking for a Kleen-axe. (the string mute that looks like a straight razor for shaving and mounts on your headstock, I think they're discontinued now though) I asked a guy in the music store if they had any. He then handed me a tissue, thinking I meant a "Cleanex".