'sblood Definition
zblŭd
interjection
God's blood.
Webster's New World
Used as an oath.
American Heritage
Origin of 'sblood
-
Shortened from God's blood. In medieval times, people would curse on God's body parts rather than breaking the third commandment (Do not use the Lord's name in vain oaths). In this case, the exclamation refers to Christ's blood shed during the crucifixion and commemorated by the drinking of wine during communion.
From Wiktionary
Shortening of God's blood
From American Heritage Dictionary of the English Language, 5th Edition