The Hebrew noun yagam (יָגָם) refers to the gain, earnings, or produce of labor — what one has worked for and accumulated. It appears in Job 20:18 in the context of the wicked man's fate: the gain he worked for will be returned without enjoying it. The word is related to the broader family of labor words (yaga, yegiya) and emphasizes the fruit or reward of effort.
Job 20 is Zophar's speech about the fate of the wicked: though the evil man may accumulate wealth, he will not enjoy his earnings (yagam). This is a wisdom theme — the disconnect between labor and enjoyment as a judgment on the wicked. Ecclesiastes explores the same problem: 'I hated all my toil in which I toil under the sun, seeing that I must leave it to the man who comes after me' (Ecclesiastes 2:18). The New Testament resolution is not the elimination of work but the reorientation of reward: true treasure is laid up in heaven (Matthew 6:20), and the labor done for the Lord is not in vain (1 Corinthians 15:58).