dead (adj.)

Middle English ded, from Old English dead "having ceased to live," also "torpid, dull;" of water, "still, standing," from Proto-Germanic *daudaz (source also of Old Saxon dod, Danish død, Swedish död, Old Frisian dad, Middle Dutch doot, Dutch dood, Old High German tot, German tot, Old Norse dauðr, Gothic dauþs "dead"), a past-participle adjective based on *dau-, which is perhaps from PIE *dheu- (3) "to die" (see die (v.)).

Meaning "insensible, void of perception" is from early 13c. Of places, "inactive, dull," from 1580s. Of sound, "muffled," 1520s. Used from 16c. as "utter, absolute, quite" (as in dead drunk, 1590s); from 1590s as "quite certain, sure, unerring;" by 1881 as "direct, straight." Dead heat, a race in which more than one competitor reaches the goal at the same time, is from 1796. The dead-nettle (c. 1400) resembles the nettle but does not sting.

Dead on is 1889, from marksmanship. Dead duck "person defeated or soon to be, useless person" is by 1844, originally in U.S. politics. Dead letter is from 1703, used of laws lacking force as well as uncollected mail. Dead soldier "emptied liquor bottle" is from 1913; the image is older (compare dead men "bottles emptied at a banquet," c. 1700). Dead man's hand in poker, "pair of aces and pair of eights," is supposedly what Wild Bill Hickock held when Jack McCall shot him in 1876. Expression not be (seen/found/caught) dead "have nothing to do with" is by 1915.

dead (n.)

Old English, "a dead person; the dead collectively, those who have died," noun use of dead (adj.).  As "the most intense or culminating point" of anything (usually something low, flat, still, or cold, as night, winter) from 1540s. To leave (someone) for dead is from late 14c.

dead (adv.)

"in a dead or dull manner, as if dead," also "entirely," late 14c., from dead (adj.). As "directly," by 1800.

Definitions of dead
dead (adj.)
the complete stoppage of an action;
came to a dead stop
dead (adj.)
not circulating or flowing;
dead air
dead water
Synonyms: stagnant
dead (adj.)
(followed by `to') not showing human feeling or sensitivity; unresponsive;
passersby were dead to our plea for help
Synonyms: numb
dead (adj.)
very tired;
I'm dead after that long trip
Synonyms: all in / beat / bushed
dead (adj.)
no longer having or seeming to have or expecting to have life;
he was marked as a dead man by the assassin
the nerve is dead
a dead pallor
dead (adj.)
not showing characteristics of life especially the capacity to sustain life; no longer exerting force or having energy or heat;
dead soil
Mars is a dead planet
the fire is dead
dead coals
dead (adj.)
unerringly accurate;
a dead shot
took dead aim
dead (adj.)
physically inactive;
Crater Lake is in the crater of a dead volcano of the Cascade Range
dead (adj.)
devoid of physical sensation; numb;
his gums were dead from the novocain
Synonyms: deadened
dead (adj.)
lacking acoustic resonance;
dead sounds characteristic of some compact discs
the dead wall surfaces of a recording studio
dead (adj.)
not yielding a return;
dead capital
Synonyms: idle
dead (adj.)
not surviving in active use;
Latin is a dead language
dead (adj.)
lacking resilience or bounce;
a dead tennis ball
dead (adj.)
out of use or operation because of a fault or breakdown;
a dead telephone line
the motor is dead
dead (adj.)
no longer having force or relevance;
a dead issue
dead (adj.)
drained of electric charge; discharged;
a dead battery
Synonyms: drained
dead (adj.)
devoid of activity; "this is a dead town; nothing ever happens here";
dead (n.)
people who are no longer living;
they buried the dead
dead (n.)
a time when coldness (or some other quality associated with death) is intense;
the dead of winter
dead (adv.)
quickly and without warning;
Synonyms: abruptly / suddenly / short
dead (adv.)
completely and without qualification; used informally as intensifiers;
you can be dead sure of my innocence
was dead tired
dead right