< Old Greek term for "servant" became the new Greek word for "slave." In Church Slavonic, the word "rab" (servant) likewise became the modern word for "slave." This is not a coincidence. Greeks believed that anyone who works for soemone else is not free. The concept of "employed" did not exist. You either worked for yourself and were free or you worked for someone else and were not free.>
O Thoulos tou Theou... as opposed to O Sklavos tou Theou....
The difference is very real as you point out.
Sometimes we kid about particularly new and overly pious and groveling converts as Oi Sklavoi tou Theou. Not very Christian of us I suppose. Got the idea from a convert, not Greek, who insisted that we were all the "slaves of God".
in some english bibles the term is more accurately put in a context of "bond servant"... a person who loves their job, their master, the respect and the position they have earned with the 'masters' family, that they bind themselves willingly to the point of death in a covenant of servanthood, for life.
Strictly a voluntary slave... who could be free, but WANTS to keep on living the 'good life' as extended family to the people who he or she serves.
Like marriage and family or a GREAT job or project with great responsibilities. Which some folks also think of as forms of "slavery."
go figure.