Wordorigins.org

Doom is a very old word, dating back to the Old English period. But the Old English dom had a differerent meaning for those in medieval England was quite different than its meaning today. It did not refer to fate or the apocalypse back then, rather it meant a law or judgment at trial.

The word appears as early as c.825 in the Vespasian Psalter with the meaning of a statute, decree, or judgment:

Bioð afirred domas ðine from onsiene his.
(Be afraid, in his presence [are] your dooms)

Heaven is a word that dates back to the Old English heofon, heben, or one of various forms that appear in extant texts from that age. Its earliest sense is that of the sky, the firmament in which the stars are placed. From Beowulf, line 1571:

swa of hefene hadre scineð rodores candel
(as from heaven, the candle of the sky clearly shines)

The plural form that is commonly used today also dates back this far. From c.825 in the Vespasian Psalter, from Psalms 8:3:

Ic gesie heofenas werc fingra ðinra
(I see the heavens, work of your fingers)

The sense meaning the abode of God, the afterlife, appears a little bit later. From a translation of the gospel of Matthew, c.1000:

Fader ure þu þe eart on heofene
(Our father, you who are in heaven)

The ultimate origin of heaven is not known. It has cognates in Low German, but the Old High German himil, from which the modern German himmel and the Dutch hemel come, the Gothic himins, and the old Norse himinn are not related.

(Source: Oxford English Dictionary, 2nd Edition)

Hell is another Old English word. It is attested to in the early ninth century, but the word and the concept is undoubtedly older, dating back to pre-Christian Germanic mythology. In Norse mythology, Hel was the goddess of the underworld. Her name and the English word for the abode of the dead are undoubtedly related, although exactly how the two senses of the word are related are unknown. Based on cognates in the various Germanic languages, historical linguists have proposed a possible root in Old Germanic, *halja, meaning something along the lines of one who covers or conceals.

The first known appearance of hell in English is c.825 in the Vespasian Psalter, a translation of Psalms 55:15:

Cyme deað ofer hie and astigen hie in helle lifgende.
(Death came over them and they went into a living hell.)

This sense is more of the abode of the dead, rather than the Christian concept as a place of punishment in the afterlife. Modern translations of the Bible tend to use the original Hebrew sheol in this passage to emphasize this difference.

The Christian sense of hell as a place of punishment and torment is attested to a few decades later in King Alfred’s translation of Boethius’s The Consolation of Philosophy, c.888:

Swa byrnende swa þæt fyr on þære helle, seo is on þam munte ðe Ætne hatte.
(As burning as the fire in the hell, it is on the mountain that is called Ætna.)

(Source: Oxford English Dictionary, 2nd Edition)

The origin of the verb to die is a bit of a mystery. One would expect that such a basic verb would go back to Old English, especially since the word has a Germanic root. But it is not attested to the Old English literature, not appearing until the early Middle English period. Instead, Old English used two other verbs, sweltan (which survives in the modern sweltering) and steorfan (the modern form of which is to starve, although in Old English it could mean death by any means, not just lack of food).

The standard interpretation is that word disappeared early in the Old English period, only to be reintroduced by the Normans. It comes from an Old Norse root deyja. The verb also died out in Gothic and the other West Germanic languages too, surviving only in the North Germanic languages.

Earl is the counterpart of churl. It originally simply denoted a man of noble birth. The word appears in several Germanic languages. Its cognates include the Old Saxon erl and the Old Norse earl, which later developed into iarl or jarl.

Like many Old English words, its date of appearance cannot be determined with any precision. The earliest known English citation is probably from sometime before 616 in the Laws of Ethelbert:

Gif on eorles tune man mannan ofsleæhþ xii scillinga gebete.
(If, in an earl’s town, a man slays a man, [he shall] pay 12 shillings.)

Earl also had a poetic sense, denoting a warrior, a brave man, or even just a man generally. Beowulf lines 356-57 read:

Hwearf þa hrædlice,     þær Hroðgar sæt,
eald ond unhar     mid his eorla gedriht
(They quickly turn to     where Hrothgar sat
old and hoary,     with his company of earls)

Following the Norman conquest, earl was formalized as a title, with a rank equivalent to that of a continental count.

(Source: Oxford English Dictionary, 2nd Edition)