Who was the man to nickname his two children Dot and Dash?

Answer 1

Thomas Edison and he's first wife Mary Edison nicknamed the two first of their three children Dot and Dash.

Marion(Dot) and Thomas, Jr.(Dash).

In he's second and last marriage he got another three children.

The nicknames is due to Edison's connection with the telegraph, it being a partial inspiration for he's future work. Dot and Dash is the two symbols used in Morse Code.

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Answer 2

Samuel Morse was the man who gave his daughters the nicknames Dot and Dash, inspired by the Morse code that he invented for telegraph communication.