apodidōmi

This verb is the ordinary word "to give" with a prefix that adds the idea of "back" or "in return." So it almost never means simply handing something over as a gift. It means giving something because it is owed: settling a debt, paying a wage, returning what was borrowed, or rendering to a person exactly what is coming to them. The thread running through every use is obligation. Someone has a claim, and the verb describes meeting that claim in full.

From that one core the New Testament fans out into several everyday shades. It pays off a loan or a fine to the last coin. It hands a borrowed scroll back, or restores stolen money several times over. It gives a required account or report when called to answer for oneself. And it covers the solemn case of recompense, where God gives each person back exactly what their life has earned, whether reward or judgment. The same word that settles a small debt between neighbors also names the final reckoning.

A few uses turn on who is acting and for what. When a person uses the verb of their own goods and takes a price in return, it becomes the normal word for selling, as when Joseph's brothers sold him or Esau sold his birthright. And in the famous saying about Caesar's coin, it carries its full weight: give back to Caesar what is already his, and to God what is God's. Across all of these the picture is steady. Something is owed, and this verb is the act of paying it.