Isaiah 48.17
Galatons 3.13
1 Corinthians 6.20
Redeemer/Redemption:   To buy back, to free from captivity by payment or ransom.
In the Law given in Leviticus chapter 25, land in Israel could not be sold permanently, but always carried with it the right of redemption, until the year of Jubilee, when all debts were canceled and all property was returned to original ownership, yet with valuation added to it.  There always was a price attached to the right of redemption, sometimes a value allowed by the Priest in accordance to the number of years left until Jubilee, sometimes a set value of 20 %.  People also could sell themselves if poverty came upon them, and then could be redeemed by extended family members, or wait until Jubilee, when all debts were cancelled.  
So in a nutshell we see the original base concept of redemption.
Job cried out in his turmoil and agony, in 19.25 “ As for me I know that my redeemer lives, and at the last, will take His stand on the earth.”  He understood the concept that Jehovah would be the one who would buy him back from whatever caused his current disaster.
In Galations 3.13 Paul wrote that the Messiah, the Christ has redeemed us, the sinners, from the curse of the Law, having become a curse for us.  This is a replacement type of redemption, having taken our place to set us free, thus the doctrine of imputation.  A ransom for our souls, His life for our life.
I Corinthians 6.20  “ For you have been bought with a price: therefore glorify God with your body.”   Again the concept of redeeming, of buying back that which was lost.  Jesus is in fact our redeemer.  The one who has purchased us with His sacrifice on the cross. 
Karl