To be a slave or bondservant of Christ is meant to imply one's gratefulness and sense of debt to Christ for bing set free. (nakedpastor.com)
A second element of these debt amnesties was to liberate bondservants — the debtor's wife, daughters or sons who had been pledged to creditors. (michael-hudson.com)
Revelation 1:1, Jude 1:1, 2 Peter 1:1, James 1:1, Titus 1:1, Philippians 1:1 Paul, James, Peter, Jude, and John and Timothy all called themselves slaves or more accurately bondservants. (nakedpastor.com)