Basic Guidelines For English Spellings
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1Chiefly with the, this, etc. Earth as opposed to heaven or the heavens; the earthly world.
2With the. The mythical abode of the dead, imagined as being under the earth, the underworld; specifically the place of the damned, hell.
Late Middle English; earliest use found in John Trevisa (c1342–?1402), translator. From lower + world.