Complex sentence: "Y.R.O." stands for "Yngwie Rip-Off", which is how producer Mike Varney referred to the track whilst still untitled, owing to its obvious similarities to Yngwie Malmsteen's "Black Star", which has an almost identical bassline.
Split into simpler sentences: Y.R.O. stands for "Yngwie Rip-Off", Y.R.O. Name. The song has obvious similarities to Yngwie Malmsteen's "Black Star", with an almost identical bassline.