moisten, water, soak
霑 centers on liquid spreading and penetrating: moistening, soaking, or being saturated with water.
霑 combines 雨 (rain) with 沾, which likely contributes both sound and the idea of soaking or moistening. The exact historical development of 沾 is uncertain.
Rain 雨 falls onto 沾, a shape associated with liquid spreading. Picture rain soaking into the ground, moistening everything it touches.
For テン, imagine ten raindrops soaking into the earth: ten -> テン, and each drop adds moisture.