Analysis of information sources in references of the Wikipedia article "Gwenhwyfach" in English language version.
According to Patrick Sims-Williams, in Welsh the "termination of -ach evokes unpleasantness" (Sims-Williams 1991:42). Therefore, Gwenhwyfar's sister Gwenhwyfach, found in the Welsh triads (Bromwich 1978) and Culhwch and Olwen (Ford 1977:131), may represent an unpleasant or evil form of Gwenhwyfar herself.
According to Patrick Sims-Williams, in Welsh the "termination of -ach evokes unpleasantness" (Sims-Williams 1991:42). Therefore, Gwenhwyfar's sister Gwenhwyfach, found in the Welsh triads (Bromwich 1978) and Culhwch and Olwen (Ford 1977:131), may represent an unpleasant or evil form of Gwenhwyfar herself.