Why "god" in godparent?

I'm looking for the etymology of words like godparent, godchild, etc. In particular, why "god" is added as a prefix? So far I haven't found an explanation. Wiktionary (for godfather) states:

From Middle English godfader, from Old English godfæder (“godfather”), equivalent to god +‎ father. Cognate with Old Saxon godfadar (“godfather”), Middle Dutch godvader (“godfather”), Danish gudfader, gudfar (“godfather”), Swedish gudfader, gudfar (“godfather”), Icelandic guðfaðir (“godfather”). Morphologically god +‎ father.

Not very helpful. Wikipedia does not provide clues either. It states:

... by the end of the 6th century, they were being noted to as "compaters" and "commaters"

which is Latin. Spanish and French terms follow a similar structure, without adding the "god" prefix (eg. "com-padre" and "co-madre" in Spanish). It seems the German word also does not contain the particle "god" in it. Any idea about the origin of such word?

Solution 1:

OED (paywalled) addresses your question,

In particular, why "god" is added as a prefix?

directly in the etymological notes pertaining to 'godfather', n. (bold emphasis mine):

In Old English, god- was prefixed to words expressing family relationship in order to reflect the view that the sponsors enter into a spiritual relationship with the baptized person and with each other (compare GODMOTHER n., GODSON n., GOD-DAUGHTER n., etc., and Old English godsibb: see GOSSIP n.).

That note covers the territory pretty well; the etymology of 'gossip' adds little, although it was of more than passing interest to me. In short, 'gossip' derives from compounding of Old English god n. and int., in the sense of

A superhuman person regarded as having power over nature and human fortunes....

and Old English sib adj. in the sense of

Related by blood or descent...

(All quoted definitions from OED.)

Solution 2:

According to the Wikipedia article on godparents:

As early as the 2nd century AD, infant baptism had begun to gain acceptance among Christians for the spiritual purification and social initiation of infants, the requirement for some confession of faith necessitated the use of adults who acted as sponsors for the child. They vocalized the confession of faith and acted as guarantors of the child’s spiritual beliefs.

Normally, these sponsors were the natural parents of a child, as emphasized in 408 by St. Augustine who suggested that they could, it seems exceptionally, be other individuals. Within a century, the Corpus Juris Civilis indicates that parents had been replaced in this role almost completely. This was clarified in 813 when the Council of Munich prohibited natural parents from acting as godparents to their own children.

Godparents, to an extent, acted as 'parents' in the eyes of god, permitted to take a shared burden of the child should something happen to the parents, for example.

While the Latin languages opted for a co-parent, the Germanic languages (including various German dialects as seen in this chart from Wikipedia ) decided to go with 'God'.

I would presume the popularity of having a non-parental godparent would be for social, but also economical reasons, such as tying family bonds and having people to look after the children.

I hope this provides some insight.

Solution 3:

I think it refers to the “role” of the godparents as God’s vicar.

The origin of godparents dates back to the early beginnings of the Christian Church. A sponsor was required for any person desirous of receiving the sacraments of baptism, holy Eucharist and confirmation. The role of the sponsor was to vouch for the person's character and to aid them as they prepared to take the sacraments.

Around 800 AD baptism of infants became commonplace and their sponsors were referred to as "patrinus" in Latin, which translates to "godfather."