Surah 83. Al-Mutaffifin, Ayah 7

According to some of the greatest philologists (e.g., Abu 'Ubaydah, as quoted in the Lisan al-'Arab), the term sijjin is derived from - or even synonymous with - the noun sijn, which signifies "a prison". Proceeding from this derivation, some authorities attribute to sijjin the tropical meaning of da'im, i.e., "continuing" or "basting" (ibid.). Thus, in its metaphorical application to a sinner's "record", it is evidently meant to stress the latter's inescapable quality, as if its contents were lastingly "imprisoned", i.e., set down indelibly, with no possibility of escaping from what they imply: hence my rendering of the phrase fi sijjin as "[set down] in a mode inescapable". This interpretation is, to my mind, fully confirmed by verse {9} below.

 Sijjîn is the name of a place (such as a confinement) in the depths of Hell.

This is a word from the same root as Sijn, a Prison. It rhymes with and is contrasted with Illiyin in verse 18 below. It is therefore understood by many Commentators to be a place, a Prison or a Dungeon in which the Wicked are confined pending their appearance before the Judgment-Seat. The mention of the Iscribed Register in verse 9 below may imply that Sijjin is the name of the Register of Black Deeds, though verse 9 may be elliptical and may only describe the place by the significance of its contents.