"Gwenog told me she often played herself. Went home in disgust."
-- extract from Gertie Keddle's diary (QA3)
Gwenog was a friend of Gertie Kettle who was interested in the wizarding game being played on Queerditch Marsh.
Gwenog is most likely a made-up Welsh name. Gwen is the feminine form of the name/word Gwyn, meaning "white". Og can mean "a harrow (type of plough)". However "og" can also be added to a noun (eg. "niwl" +og = niwlog "foggy", "cloud" cwmwl +og = cymylog "cloudy").