Douglas Harper's Etymology Dictionary
earth-mother
1870, folkloric spirit of the earth, conceived as sensual, maternal; often a translation of German erdmutter. Earth-goddess is from 1837.
Usage examples of "earth-mother".
There were river-gods, woodnymphs, fire-spirits, elves, wills o' the wisp, pixies, chthonic deities, earth-mothers, thunder-demons, even a few metaphysical abstractions huddled wretchedly at the back and insisting on soft lavatory paper.