E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
At the first blush. At the first glance; speaking off-hand without having given the subject mature deliberation. The allusion is to blushing at some sudden or unexpected allusion; the first time the thought has flashed into your mind.
To put to the blush. To make one blush with shame, annoyance, or confusion.
England might blush in 1620, when Englishment trembled at a fools frown [i.e. James I.], but not in 1619, when an enraged people cut off his sons [Charles I.] head.Wendell Phillips: Orations, p. 419.