Whereas in modern parlance a bruise is viewed as a minor injury and is almost a positive image (e.g., “he escaped with only a few bruises”), in the Bible the image is stark and powerful, with connotations of serious and repeated injury that is virtually a death blow. No single biblical term names the image; instead a number of words encompass the semantic idea of bruise, all of them denoting injury, pain and wound.
(ed. Leland Ryken, James C. Wilhoit, Tremper Longman III, Dictionary of Biblical Imagery, Inter-Varsity Press, Downers Grove, Illinios, 1998, pg 127)
Now we can read Isaiah 53:5 and Genesis 3:15 with greater appreciation.
And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.