3John 1:12

Δημήτριος (Dēmētrios) is derived from Δημήτηρ (Demeter), the ancient Greek goddess of agriculture and the harvest. The name Δημήτηρ is composed of δᾶ (da), a pre-Greek root meaning "earth," and μήτηρ (mētēr), meaning "mother."

The word Δημήτηρ in the context of Greek culture extended to signify things related to agriculture, such as "the harvest" or "grain" (e.g., Δημήτριος καρπός, meaning "fruit of Demeter" or "grain"), and she was often invoked in agricultural rituals and oaths. Δημήτηρ was considered the protectress of the earth's fertility and the sustenance it provides.

In later contexts, the name also referred to the worship of Isis in Egypt (syncretic religious practices in the Hellenistic period), with Δημήτηρ Αἰγυπτίη (the "Egyptian Demeter") referring to Isis, the Egyptian goddess who shares many attributes with Demeter, particularly in her role as a mother and goddess of fertility.

(cf. Bailley Δη·μήτηρ)