a square thing

[vil]

Dear teachers,

Would you be kind enough to give me your considered opinion concerning the interpretation of the expression in bold in the following sentence?

I have done the square thing by my pard – my pard, that always treated me white. (E. Seton-Thomson, “Lobo: the King of Currumpaw and other Stories”)

a square thing = loyal act, loyal proceeding

V.

[konungursvia]

I think you're on the right track, though I have my doubts that the quote is a bit of a caricature (white/right).

To square can mean to reciprocate or repay, so being "square" can mean "even" or "equal"; therefore, doing the square thing can mean the appropriate thing to repay some debt of gratitude.