What is the linguistic meaning of 'Rahn' (pledge/mortgage)?

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Linguistically, Rahn signifies firmness and permanence. It is stated that water may be described as 'rahin' (stagnant) and blessing as 'rahinah' (firm, perpetual). Another opinion holds that it derives from the meaning of detention or confinement, supported by the Quranic verses: "Every person is a pledge for what he has earned" (Quran 52:21) and "Every soul is a pledge for what it has earned" (Quran 74:38).