といえどもEven (if), Although, Even though

These are both formal/written-style expressions that have the same fundamental meaning of 'even if one says'. In practice, both are used as a literary way to say 'although’, even if there is no explicit intention of quoting something that was said, e.g. ここは治安がいい(といえども・とはいえ)油断してはいけない ('Even though it's safe here, you mustn't be careless.').

といえども is essentially a more formal/written-style variant of the more casual/colloquial と言っても, with both meaning 'even if one says'. Though they can overlap in usage, と言っても is perhaps more commonly used when referring to something actually said, e.g. 安いと言っても5000円はする ('Although I say it's cheap, it does cost 5,000 yen.'), while といえども is often used figuratively with no explicit sense of quotation, e.g. 名人(だ)といえども失敗する時もある ('Although he's a master, he sometimes fails.').