to put out the tongue
舚 centers on the action of sticking out the tongue.
舚 is a phono-semantic compound: 舌 (tongue) suggests the meaning, while 詹 likely contributes the sound テン. The exact historical development is uncertain.
The left side 舌 is the tongue, and the right side 詹 looks like a face with an open mouth. Imagine a tongue sticking out from that mouth.
For テン, picture the number ten (テン) tongues all sticking out at once: ten -> テン, and each tongue is extended.
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