In bgp_sovc.h, at the top, it says:
BGP Secure Origin Validation Code
Further down in the file, it says:
BGP Secured Origin Validate Cache – SOVC
Basically, the router downloads the VRPs from the RPKI server, using RFC 6810.
Then it uses the downloaded VRPs to validate received routes using RFC 6811.
SOVC refers to the code that does that.