where do these creatures get their name from?
Greek "árthron" and "pous"
Arthropod
The word "arthropod" comes from the Greek "árthron", "joint", and "pous" (gen. "podos (ποδός)"), i.e. "foot" or "leg", which together mean "jointed leg". 
what is ocean sunfish? One of the heaviest known bony fishes in the world. what do they survive on? Small fish, fish larvae, squid, and crustaceans, etc. what is the last one? Large and diverse arthropod taxon. can the term that you just mentioned be classified? Yes, subdivided into five subphyla. can you name any? UNANSWERABLE
wiki:16876675
Arthropod [SEP] Etymology
The word "arthropod" comes from the Greek "árthron", "joint", and "pous" (gen. "podos (ποδός)"), i.e. "foot" or "leg", which together mean "jointed leg". The designation "Arthropoda" was coined in 1848 by the German physiologist and zoologist Karl Theodor Ernst von Siebold (1804–1885).