such-and-such a place; some place or other
Used when referring to a place whose name is not specified or is unimportant, similar to 'somewhere' but with a nuance of 'a certain place'.
彼はどこそこの出身だと言っていた。
He said he was from such-and-such a place.
どこそこに行く
I have plans to go to some place or other.
Usually written in kana; the kanji form 何処其処 is rare and mainly encountered in older or literary texts.
Kanji spelling is uncommon; learners will almost always see the kana form.
Compound of どこ (where) and そこ (there), literally 'where-there', used to refer to an unspecified place.