The Hebrew verb gamar means to complete, to finish, to come to an end, or to accomplish fully. It carries the sense of something being brought to its full conclusion — whether a task, a plan, or even a person's resolve.
In the Psalms, gamar is used with surprising personal urgency — the psalmist confesses that the faithful are failing or coming to an end (Psalm 77:8), or calls on God to bring to completion what He has begun. This shows the word's range: endings can be tragic (the end of the righteous) or triumphant (the completion of God's purposes).
Theologically, gamar points to the faithfulness of God who completes what He starts (cf. Philippians 1:6 in the NT). It also warns against prematurely concluding that God has abandoned His people.