wreg-
“to track, to pursue”pursue, drive, track
Root for tracking/pursuing, yielding English wreak, wreck, urge, Latin urgere.
Discussion
The PIE root *wreg- (to track, to pursue, to drive forward) produced vocabulary for both physical tracking and legal prosecution — the concept that to pursue someone through the wilderness and to pursue them through the courts are aspects of the same activity.
English wreak (OE wrecan, "to drive out, to punish, to avenge") continues the root natively: to wreak vengeance is to drive punishment forward against an offender. The related wreck (originally "something driven ashore" — a ship driven by storm) preserves the physical-driving sense.
German rächen (to avenge) confirms the Germanic cognate. Old Norse reka (to drive, to pursue) shows the Scandinavian form.
Latin urgēre (to press, to drive, to urge) may be connected through a variant formation, giving English: urge (to drive forward), urgent (pressing, driving), and the combining form -urge in surge (sub-urgēre, to rise from below by driving force).
The root connects to *sekʷ- (to follow, to pursue — see the sequel/sequence family) as part of the PIE vocabulary of pursuit. Where *sekʷ- emphasised following in sequence, *wreg- emphasised the driving force of the pursuit — the active, aggressive chasing rather than the passive following.
Notes
Pokorny 1181. English wreak, wreck, urge.