Why does the Bible use the word redemption?
Scripture uses redemption because God had to buy back what was once His but was lost. A purchase back presupposes prior ownership and loss; Satan gained control, so God pays the price of redemption—first for Israel nationally and for the whole world generally.
Les explains that the word redemption must be used because you do not buy something back unless you once owned it and lost it. He illustrates this with a hock shop: an item was yours, you hocked it, took a loan against it, and the shop took control; you cannot regain control until you pay the redemption price. In Scripture, God had to pay the price of redemption because what was once His, He lost; Satan picked it up and holds it tightly until God pays. This applies first to Israel nationally and then to the whole world in general. Israel was lost when Joseph's brothers sold him into slavery; though sinful and wrong, it caused God to lose control of the embryonic nation. They ended up in Egypt for 215 years under the Egyptian yoke, then came out as recorded in Exodus.