For the world would she not have her weakness suspected, and yet, unequal to an absolute falsehood, was constrained to acknowledge that the wind had kept her awake a little.
…and character, misled by the rhodomontade of his friend to believe his father a man of substance and credit, whereas the transactions of the two or three last weeks proved him to be neither; for after coming eagerly forward on the first overture of a marriage between the families, with the most liberal proposals, he had, on being brought to the point by the shrewdness of the relator, been constrained to acknowledge himself incapable of giving the young people even a decent support.
There are no more uses of "constrained" in the book.
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...it is very grievous to be constrained to keep our hands off such a dainty dish as Narnia.
C.S. Lewis -- The Horse and His Boy
It seemed that we were all cloaked in an unwelcome garment of racial difference that constrained, confined, and restricted us.