What is the reasoning behind picking お or ご as an honorific prefix?


We've learnt that お is used for 訓読み and ご is used for 音読み. I want to know why
we use お上手 and お電話. Why can't we use ごじょうず and ごでんわ？




Just based on a feeling,

Native Japanese speakers seem to differentiate お and ご usage based on whether
or not they feel that that word is "formal" or not and whether they feel it's
"Chinese" or not.

Two examples:

1) Even though everyone knows that 電話 is a Chinese word, ご電話 would sound silly
because noone feels that the phone is a formal thing. In this case...

[code]

    Chinese + Not Formal = お   
    
[/code]

2) お返事・ご返事 - When you use お to make a native verb honorific, it often turns
into a noun that ends with an い sound, like お書きになる. 返事 also ends in an い
sound, so maybe it's one of those verb-noun-honorific thingies, or was it
Chinese? Aw, crap I gotta type this email real fast or I won't get to go home
on Sunday...

[code]

    Formal / Was that Chinese again? = wtf?
    
[/code]

Just from my experience, I would also say that Japanese honorifics vary in
both "formality" and "Chinese-yness".

>   1. お is medium well formality hold the Chinesey （お宝・お電話・お返事・お髭・お世話）
>   2. ご is well done formality with a big side of Chinesey （ご注文・ご連絡・ご返事）
>   3. 御（おん） is very well done formality with some Chinesey （御嶽山・御中・御礼）
>   4. 御（み） is maximum formality, hold the Chinesey with a divine respect
> remoulade （み位・巫女）
>   5. 御（ギョ） is a melted Chinesey sandwich on toasted Imperial rye （御意・御感）
>

  * ご and ギョ are both 音読み of the Chinese word 御
  * お・み・おん are some form of a very old honorific word called おおむ which may be a verb meaning "I respect you big-time"

But the answer to your question, "why we can't use one with the other" is
probably just because that would be going against the consensus decision of
how formal or Chinesey a word is considered to be.

9 times out of 10 though, native speakers (of any language!) are just copying
what they've heard or seen before.

