Where does “南蛮鴃舌” come from?

南蛮鴃舌 (Japanese) comes from Japanese 舌, from Old Japanese した, from Translingual − — A long signal, used to form Morse code text, together with. (a short signal).

Ancestry of “南蛮鴃舌”, step by step

Step	Language	Word	Meaning
1	Japanese	舌	tongue
2	Old Japanese	した	—
3	Translingual	−	A long signal, used to form Morse code text, together with. (a short signal)

Every word from Translingual − →Every word from Old Japanese した →Every word from Japanese 舌 →