adverb
Used to refer vaguely to something already mentioned or understood from context, often when summarizing or avoiding repetition.
彼はかくかくの理由で遅れたと言った。
He said he was late for such and such reasons.
かくかくしかじかの事情で、今日は休みます。
Due to various circumstances, I'll take the day off today.
Reduplication of the classical demonstrative かく (thus, in this way). The exact historical derivation is uncertain, but it has been used since classical Japanese to refer vaguely to previously mentioned matters.