I can give you some insight for that word actually! Verus, or veritas, are both different forms of the latin word for truth. Veritaserum would be a play on words fusing the latin word with the english "serum".
Astrum is a latin word for the stars, and I added verus on account of the unfortunate fact that someone had taken my standard username before I could get a hold of it. True Star would be how it comes out in english I suppose.