expression, suru verb (precursor)
stubbornly refuse to admit one is wrong
A classical idiomatic expression used to describe someone who obstinately refuses to acknowledge their mistake, often by making unreasonable excuses. The literal image is of rinsing one's mouth with a rock and using a flowing stream as a pillow, implying absurd contrariness.
彼は石に漱ぎ流れに枕すような言い訳をして、自分の非を認めようとしなかった。
He made excuses as absurd as rinsing his mouth with a rock and resting his head in a stream, refusing to admit he was wrong.
The exact origin is uncertain, but the phrase is a classical Chinese-derived idiom (故事成語) that uses hyperbolic imagery to depict stubborn refusal to admit fault.