Despite its proximity to the Medway, Wateringbury probably has nothing to do with water from an etymological point of view. It was first recorded in the late tenth century under the delightfully complicated name of Uuotryngebyri and its original meaning is unclear. The -bury is likely the Old English burh or stronghold, and -ing- may well come from an Old English word indicating followers or family, suggesting a meaning along the lines of stronghold of Ohtheres family. Other possibilities put forward include stronghold of the swine pasture.
Westerham is a village which has been recorded at least as early as the ninth century and was mentioned in the Domesday Book in a Norman form, Oistreham. Ham is an Old English word meaning a village or homestead, and so Westerham is literally a westerly homestead.