Sicilian Defence: 4.Qd4

Does any one know the name of the variation: 1.e4 c5  2.Nf3 d6  3.d4 cd4  4.Qd4

Or if there was a grandmaster in particular who introduced or pioneered it in the early years?

It is widely played at the top level..........but does it have a name?.............and who first played it seriously?

I have seen old books from the 90s call it the Moscow Variation, but then the last 20 years, "Moscow" meant 3.Bb5+ (after 2...d6).

Quite frankly, what matters is the ideas, not the name.  Are you going to play iy or not play it based on its name?  There are no books on this line by itself.  There are repertoires that feature this, but then you have 2...Nc6, 2...e6, etc to deal with.  I do not recall if I saw a chessbase product or a recent book that recommends that line, but they do not have a name other than 4.Qxd4.

That said, if you like the positions in that line, just play it.  Who cares what it is called?  It could be the Moscow or Beijing or Tokyo or Oreo variation.  Outside of that recent finding that I do not totally recall and Chess Publishing section 5, I am not sure where else you would find info on that line except Black Anti-Sicilian repertoires, which will just give Black a single line against it.

I am not looking for lines or to play the variation. I was just curious who pioneered it in its early days

In case anyone else is interested later, I now know that it is called the Chekhover Variation (or sometimes the Hungarian Variation, though that can refer to something else as well).

I've played it quite a lot in blitz. What tends to happen is shown below. It's amazing how often Black players weaken their position with ...e5. I know there are good ...e5 lines in the Sicilian, but this doesn't seem to be one of them.