Significance of ところ in set phrases ところで and ところが


In two conjunctions 「ところで」 and 「ところが」 that mean "by the way / incidentally"
and "however / nevertheless" respectively, what is the significance of the
word 「ところ」?

How does ところ + で give the nuance of "this is an extra information", while ところ
+ が give the nuance of "this is contrary to the fact"?

What is the place referred by ところ in both conjunctions?




As others have stated, the reasons why there's a ところ in ところが and ところで are
entirely historical. It probably had a more literal meaning in the past, but
now its became part of a frozen expression, where the lexical value (the
meaning) is assigned to the entire expression, and its parts don't matter much
anymore. The situation here is really no different than "by the way" which
Dave gave out as an example.

But if you do want to delve into the historical explanation (and I guess you
do), it's probably something along these lines: ところ has already gotten a
generic meaning by the time of the earliest written Japanese, and when it was
used with a particle, these meanings combined into something new.

Now I'll try to give more specific details for each expression. Note that
everything here is my theorizing, mostly based on what I've found in my Kokugo
dictionaries (especially Kōjien, which lists the senses for each entry in
their historical order, and attempts to provide the earliest examples for each
sense).

## ところが

This is one seems easier to explain on the surface level: it's just ところ in its
generic meaning, referring to what was previously said, and then we have the
conjunctive particle が, which may be used in the meaning of the English "but".
There truth is probably quite more complex, however.

It seems like ～ところが was originally used only after full clauses, especially
verbs conjugated in the past form (～したところが). The meaning of が here was not
only contrastive ("but") - it could equally be used as a connective ("and"),
just like が is used today in both capacity. This whole expression translated
more or less to: "did ~ and" or "did ~ but". The more literal meaning was
something like "this is the point that X was done. And/but then ...". But this
is quite a cumbersome translation of a very faint shade of meaning that
eventually faded away. :)

## ところで

Since ところ with a verb in the past tense already has the grammatical meaning of
"the point when the action is completed", ところで may have been used first in the
meaning of "with that having been done, ...", and Kōjien indeed list this
usage. Eventually, this usage was specialized to mean "with that having been
said, let's move to something else".




As others have stated, the reasons why there's a ところ in ところが and ところで are
entirely historical. It probably had a more literal meaning in the past, but
now its became part of a frozen expression, where the lexical value (the
meaning) is assigned to the entire expression, and its parts don't matter much
anymore. The situation here is really no different than "by the way" which
Dave gave out as an example.

But if you do want to delve into the historical explanation (and I guess you
do), it's probably something along these lines: ところ has already gotten a
generic meaning by the time of the earliest written Japanese, and when it was
used with a particle, these meanings combined into something new.

Now I'll try to give more specific details for each expression. Note that
everything here is my theorizing, mostly based on what I've found in my Kokugo
dictionaries (especially Kōjien, which lists the senses for each entry in
their historical order, and attempts to provide the earliest examples for each
sense).

## ところが

This is one seems easier to explain on the surface level: it's just ところ in its
generic meaning, referring to what was previously said, and then we have the
conjunctive particle が, which may be used in the meaning of the English "but".
There truth is probably quite more complex, however.

It seems like ～ところが was originally used only after full clauses, especially
verbs conjugated in the past form (～したところが). The meaning of が here was not
only contrastive ("but") - it could equally be used as a connective ("and"),
just like が is used today in both capacity. This whole expression translated
more or less to: "did ~ and" or "did ~ but". The more literal meaning was
something like "this is the point that X was done. And/but then ...". But this
is quite a cumbersome translation of a very faint shade of meaning that
eventually faded away. :)

## ところで

Since ところ with a verb in the past tense already has the grammatical meaning of
"the point when the action is completed", ところで may have been used first in the
meaning of "with that having been done, ...", and Kōjien indeed list this
usage. Eventually, this usage was specialized to mean "with that having been
said, let's move to something else".

