What does "できたれば" mean in the following sentence?
予とてわかっておる……目の上の瘤が取れ、心持ちに余裕ができたればこそそんな思いも浮かぶのだ。かつては考えもせなんだことを
I assume it's related to できる but why is it not できれば?
This たれ is the realis-form (已然形) of たり, which is an auxiliary in classical/archaic Japanese. This たり is like ている in modern Japanese, and 已然形 + ば means "because". So できたれば translates to できているから in modern Japanese. (Note that this れば is not "if"; see the last link below for details.)
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