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〜といえども: even if; although
N1 · 04 Concession and contrast
Says that even in a case of X, the usual expectation does not hold.
Noun or clause + といえども. Formal. Often with 例外 or high status: 子供といえども. The second half is a surprising or firm statement. Compare 〜とはいえ, which says "although it is true".
Examples
専門家といえども、間違えることはある。
Even an expert makes mistakes.
子供といえども、責任は取らなければならない。
Even a child must take responsibility.