river in Hebei province
泜 is a rare kanji that names a specific river in Hebei province. Its meaning is purely geographical and does not extend to general water concepts.
泜 combines 氵 (water) with 氐, which likely contributes the sound. It was created as a specific river name, and the exact historical development of the phonetic component is uncertain.
The water radical 氵 beside 氐 points to a river. Picture the 氵 as the flowing water of the 泜 River in Hebei.
For テイ, imagine a tea (ティー) plantation along the banks of the 泜 River: tea -> テイ, and the river waters the tea plants.
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