Dear Cecil,
I strongly support the theory of the origin of “Dad” as some product of childish speach.
However, something perhaps more interesting is the origin of the word “Papa”, or just “Pa”: As scholars all know, “father” in Greek is “Pateras”. The form for this has then spread throughout the Western world, Italian = “Babbo” or “Pappo”, French = “Papa” (with a stress on the last “a”), Swedish = “Pappa” (formal “Far”, or old form “Fader”). Even the English “father” can be derived from the Greek origin. Only exception to this “rule” that I personally can think of quickly would be the Finnish Father = “Isä”, but then again - Finnish is an exceptional language in every aspect!
I live in hong Kong at this time and was astonished when I first learned that in both Cantonese and Manadarin chinese, the word for “Father” is (you guessed it!) “Ba” or “Baba”. (Just by curiosity, "Mother is “Ma” in Cantonese). Clearly, most Cantonese have not studied Greek (at that pre-school age when this word becomes of daily use at least), but still they as well use this “universal” connotation for their parent(s). The same connotations can be found throughout other cultures all over the world as well. clearly, a child would have no problem forming other combinations of sounds than the above mentioned forms, so how come that in almost all cultures, we have ended up with more or less the same thing ?
I do not have the answer to as why, maybe you could look in to it ?
Ingemar Lampa
Hong Kong