According to dictionary.reference.com, the origin and history of “mortgage” is:
1390, from O.Fr. morgage (13c.), mort gaige, lit. “dead pledge” (replaced in modern Fr. by hypothèque ), from mort “dead” + gage “pledge;” so called because the deal dies either when the debt is paid or when payment fails. O.Fr. mort is from V.L. *mortus “dead,” from L. mortuus, pp. of mori “to die.
In 2008, we bought our first house and committed ourselves to such a pledge. I don’t know why I didn’t think about the meaning of the word before we went ahead with the purchase.