"son" is a lot easier to say than "daughter"...and it sounds less formal too. But then again, who am I to know?

Maybe you know more than the rest of us know, Gonoldothrond*.

Akio Morita, the founder of Sony Corp., is said to have come up with the name SONY after visiting America and falling in love with the sound of "sonny".

I can't imagine anyone calling a company with global ambitions "Daughter" or any variation of "Daughter". [* Or "Gonoldothrond" either. BTW is "Gonold" your first name, as in "Gonold o'Thrond"?]

Come to think of it, there is no diminutive for "daughter" as there is for "son".

Sometimes the answer to a tough question is a lot more obvious than we expect. Good call!