Folds in folds of his flesh translates a noun related to the verb “to fall,” and so is literally “what falls down.” New English Bible understands this to mean “underbelly.” Folds of his flesh gives the picture of a fat animal with rolls of flesh. But the poet says that even these parts, which in another animal may be flabby and soft, are compact, or form a solid mass. The verb is the same as in 19.20 and 31.7. Good News Translation “skin” is not a suitable model to follow.

The second line emphasizes again the hardness of Leviathan’s flesh. Cast translates the verb used for casting or molding hot metal, and so the thought is that his flesh has been molded on him, like pouring hot liquid metal into a mold. This is a figure used to express hardness, and Good News Translation expresses the figure as a simile which is clear: “it is as hard and unyielding as iron.” Verse 23 may also be expressed, for example, “Even the meaty parts of his body are as hard as cast metal” or “Even the softest parts of his body are like iron.”

Quoted with permission from Reyburn, Wiliam. A Handbook on Job. (UBS Helps for Translators). New York: UBS, 1992. For this and other handbooks for translators see here .