Theotokos is an adjectival compound of two the Greek words Θεός "God" and τόκος "childbirth, parturition; offspring". A close paraphrase would be "[she] whose offspring is God" or "[she] who gave birth to one who was God". The usual English translation is simply "Mother of God"; Latin uses Deipara or Dei Genetrix.
The Church Slavonic translation is Bogoroditsa (Russian/Serbian/Bulgarian Богородица). The full title of Mary in Slavic Orthodox tradition is Прест҃а́ѧ влⷣчица на́ша бцⷣа и҆ прⷭ҇нод҃ва мр҃і́а (Russian Пресвятая Владычица наша Богородица и Приснодева Мария), from Greek Ὑπεραγία δεσποινίς ἡμῶν Θεοτόκος καὶ ἀειπαρθένος Μαρία "Our Most Holy Lady Theotokos and Ever-Virgin Mary". German has the translation Gottesgebärerin.
"Mother of God" is the literal translation of a distinct title in Greek, Μήτηρ του Θεού (translit. Mētēr tou Theou), a term which has an established usage of its own in traditional Orthodox and Catholic theological writing, hymnography, and iconography.
In an abbreviated form, ΜΡ ΘΥ (М҃Р Ѳ҃Ѵ), it often is found on Eastern icons, where it is used to identify Mary. The Russian term is Матерь Божия (also Богома́терь).
Variant forms are the compounds Θεομήτωρ (translit. Theomētor; also spelled Θεομήτηρ, translit. Theomētēr) and Μητρόθεος (translit. Mētrotheos), which are found in patristic and liturgical texts.
The theological dispute over the term concerned the term Θεός "God" vs. Χριστός "Christ", and not τόκος (genetrix, "bearer") vs. μήτηρ (mater, "mother"), and the two terms have been used as synonyms throughout Christian tradition. Both terms are known to have existed alongside one another since the early church, but it has been argued, even in modern times, that the term "Mother of God" is unduly suggestive of Godhead having its origin in Mary, imparting to Mary the role of a Mother Goddess. But this is an exact reiteration of the objection by Nestorius, resolved in the 5th century, to the effect that the term "Mother" expresses exactly the relation of Mary to the incarnate Son ascribed to Mary in Christian theology.[c][d][e]