そこで、「あの傘はたった一つしかない家宝なので、お殿様といえど譲るわけには参りませんと断りました」
Therefore, I refused, saying, "That umbrella is my only family heirloom and, even if you were a lord, I would not give it away."
われわれは何人といえど、自分が属している社会という組織から自分を切り離すことは出来ない。
No matter how many of us there are, we cannot separate ourselves from the social organization to which we belong.
From Jisho.org, archaically, ど collocated with the stem of a verb in ば form. Seemingly, this happens to be the case with といえど because the stem of the affirmative ば form of いう is いえ, which, judging from the examples above, changes the meaning of という to a conditional one. Hence, the question: can we think of といえど as という + ど ?