drain between fields, irrigation
甽 centers on water channels in farmland: a drain between fields or an irrigation ditch that moves water through crops.
甽 combines 田 (field) and 川 (river/stream), suggesting a water channel in a field. The exact historical development is uncertain, but the component combination fits the meaning of field drainage or irrigation.
A field 田 with a river 川 running through it: that river is actually a narrow drain or irrigation channel between the crops.
For ケン, picture a farmer named Ken digging a drain between his fields: Ken -> ケン, and his work keeps the fields irrigated.