Percival is often explained as "pierce the valley," though that reading may be a later poetic gloss rather than the name's true root, which remains genuinely unclear. What has stuck regardless is its association with a knight defined by a long, uncertain search -- a name tied to quest more than arrival.
A Planet in an Angle doth more effectually produce his effects, but remiss in Cadent Houses. - William Lilly (1602.-1681.)