Shinwonryu is a Shinsoo manipulation style which can only be mastered by "Those who have opened the door" (most likely the Irregulars).
This technique compresses Shinsoo around onto a single point and releases it as a huge explosion. According to the "God" of guardians, this technique is far above what ordinary Regulars can hope to achieve; a small amount of Shinsoo can cause great destruction. A tired Baam, using a single baang of this technique on a pack of big Crystal Shards, was able to utterly annihilate all of them in an instant lending credence to the sheer power of the technique.
Zahard can empower himself by having Shinwonryu explode inside him.  Baam feels that it was different from other internal quality shinsoo control like Redan. 
SIU based the visual on "light" rather than "water" for shinsoo.
The technique has been shown to be able to surpass the spell endowing immortality to 43rd Floor inhabitants. This has been assumed by the fandom to be a result of the way the shinsoo is controlled.
The meaning of 신원류 ("shinwonryu") is ambiguous as SIU has not yet provided the corresponding hanja spelling, when several alternatives are possible. In particular, 신 ("shin") is likely 神 ("god/divine", which could also refer to shinsoo), and 원류 ("wonryu") could be either 圓 ("won") and 流 ("ryu") ("circle style") or 流派 ("wonryu") ("origin"). It is likely that SIU is playing with several of the meanings.
Data Zahard calls Baam's earlier use of this technique (before he started using it with orb) as a sloppy 'imitation' of Shinwonryu, one he learned from God of Guardian. This suggest that this technique, while by itself powerful, should not be used as it is. Koon Eduan reinforce this by saying that Shinwonryu can only be used when one had already found quality of shinsoo that suits them.
↑Post by Cletus originally at bato.to: [... 신원류 can be interpreted as] 신원류(神流派) = 神(shin) + 流派(wonryu): 神 (god, but it is better be shinsoo in this case.); 流派 (wonryu) [noun] 1. The main stream of river (synonym: 水源: a source of water supply) / 2. Nature of matter/phenomenon (synonym 淵源: an origin, a source, a beginning). So it has nothing to do with that blackhole whatever.