The story
- Old English · inherited fromwang“field”
- Old English · inherited fromwet“wet”
- Old Norse · derived fromvaett-vangr“field for the trial of a legal action”
- English todayWetwang
From either Old Norse vaett-vangr (“field for the trial of a legal action”) or Old English wet (“wet”) + Old English wang (“field”), as compared to the nearby dry field at Driffield
Etymology from Wiktionary, CC BY-SA 4.0.