I give up; there's nothing more to be done
A classical, formal expression of resignation or helplessness, often used in literary or dramatic contexts. It conveys that all efforts have been exhausted and the situation is beyond one's control.
Having come this far, I give up; there's nothing more to be done.
He sighed deeply and muttered, 'I give up.'
From classical 已みぬるかな: 已み is the continuative form of 已む, ぬ is the perfective auxiliary, ぬる its attributive form, and かな an exclamatory particle. It expresses resignation that something is finished or beyond remedy.