"I believe the council of Ephesus in 431 AD also played a major role, there Mary was proclaimed the Theotokos. Instead of translating the term 'God-bearer' it was popular to translate it 'Mother of God'."
The difficulty with an English translation of Theotokos as "God-bearer" is that it doesn't really communicate the full meaning of the term.
Here's an entry from Wikipedia (I use it because it's easily accesible and the information found here is generally in agreement with other authorities):
"Theotokos is a compound of two Greek words, Θεός God and τόκος parturition, childbirth."
Thus, it would be better to translate as "God-birther." Mary is the woman who gave birth to God. That is the doctrine pronounced at Ephesus.
Typically, we call women who give birth to a child the mother of the person born. Thus, as Mary is the "God-birther," "Mother of God" works equally well.
This is especially so as Mary is biologically the mother of Jesus, not merely a surrogate (an idea likely beyond the ken of Christians up until relatively recently), Who is God.
sitetest
The problem occurs when the term "Mother of God" is the accepted translation, it implies all kinds of things that just aren't true. For example, that Mary as mother of God has authority over God. Another example that Mary is the "Queen of Heaven", or "Queen mother of Heaven", or Mary is the wife of the Holy Spirit since it was through the Holy Spirit that Jesus was conceived.
If all these things become acceptable then believing she can magnify prayers, or aid in your salvation easily follow. I find no evidence of any of that in Scripture.
The term God-bearer is more on the mark in that Mary was blessed to be used by God for His plan of salvation. Mary does not bestow blessings on others because of this.