First, Let's say the random word machine gave us the word "MEGADON". Do you want a prefix before megadon like Lil, Big or young or do you rather keep it singular?
Second, let's go to the search bar and type the name, but make sure to put the keywords after your idea to see if it's not already being used. So it would look like "Lil Megadon SoundCloud" or Megadon music or Megadon on Spotify. Keep generating new random words if your rap names are taken. For instance: if you searched Lil Xuzki music, our artist comes up, BUT take out the "X" and see what happens. Now you know the secret of keywords in google.