What is "mongewell"

Mongewell (first syllable rhymes with sponge) is a village in the civil parish of Crowmarsh, about south of Wallingford in Oxfordshire. Mongewell is on the east bank of the Thames, linked with the west bank at Winterbrook by Winterbrook Bridge. The earthwork Grim's Ditch, now part of The Ridgeway long-distance footpath, passes through the northern part of it and is a scheduled ancient monument.