Rhys is a short, sturdy Welsh name traditionally linked to ardor or enthusiasm -- passion in the sense of drive rather than volatility. It's often chosen for its brevity as much as its meaning, a name that doesn't need embellishment to carry its intensity.
Every beginning when the Moon shall be joined to a Retrograde planet will soon be destroyed, and if she shall be otherwise impedited, the mischief will happen the sooner. - William Lilly (1602.-1681.)