hard (adj.)

Old English heard "solid and firm, not soft," also, "difficult to endure, carried on with great exertion," also, of persons, "severe, rigorous, harsh, cruel," from Proto-Germanic *hardu- (source also of Old Saxon hard, Old Frisian herd, Dutch hard, Old Norse harðr "hard," Old High German harto "extremely, very," German hart, Gothic hardus "hard"), from PIE *kortu-, suffixed form of root *kar- "hard."

Meaning "difficult to do" is from c. 1200. Of water, in reference to the presence of mineral salts, 1650s; of consonants, 1775. Hard of hearing preserves obsolete Middle English sense of "having difficulty in doing something." In the sense "strong, spiritous, fermented" from 1789 (as in hard cider, etc.), and this use probably is the origin of that in hard drugs (1955). Hard facts is from 1853; hard news in journalism is from 1918. Hard copy (as opposed to computer record) is from 1964; hard disk is from 1978; the computer hard drive is from 1983. Hard times "period of poverty" is from 1705. Hard money (1706) is specie, silver or gold coin, as opposed to paper. Hence 19c. U.S. hard (n.) "one who advocates the use of metallic money as the national currency" (1844). To play hard to get is from 1945. Hard rock as a pop music style recorded from 1967. To do something the hard way is from 1907.

hard (adv.)

Old English hearde "firmly, severely," from hard (adj.). Meaning "with effort or energy, with difficulty" is late 14c.

Definitions of hard
hard (adj.)
took a hard look
a hard bargainer
hard (adj.)
resisting weight or pressure;
hard (adj.)
very strong or vigorous;
a hard left to the chin
Synonyms: knockout / severe
hard (adj.)
characterized by effort to the point of exhaustion; especially physical effort;
hard labor
Synonyms: arduous / backbreaking / grueling / gruelling / heavy / laborious / operose / punishing / toilsome
hard (adj.)
produced without vibration of the vocal cords;
Synonyms: unvoiced / voiceless / surd
hard (adj.)
(of light) transmitted directly from a pointed light source;
Synonyms: concentrated
hard (adj.)
(of speech sounds); produced with the back of the tongue raised toward or touching the velum;
Russian distinguished between hard consonants and palatalized or soft consonants
hard (adj.)
given to excessive indulgence of bodily appetites especially for intoxicating liquors;
a hard drinker
Synonyms: intemperate / heavy
hard (adj.)
being distilled rather than fermented; having a high alcoholic content;
hard liquor
Synonyms: strong
hard (adj.)
unfortunate or hard to bear;
had hard luck
Synonyms: tough
hard (adj.)
dried out;
hard dry rolls left over from the day before
hard (adj.)
not easy; requiring great physical or mental effort to accomplish or comprehend or endure;
why is it so hard for you to keep a secret?
Synonyms: difficult
hard (adv.)
with effort or force or vigor;
pressed hard on the lever
the team played hard
hit the ball hard
slammed the door hard
worked hard all day
hard (adv.)
with firmness;
held hard to the railing
Synonyms: firmly
hard (adv.)
earnestly or intently;
stared hard at the accused
thought hard about it
hard (adv.)
causing great damage or hardship;
industries hit hard by the depression
Synonyms: severely
hard (adv.)
slowly and with difficulty;
prejudices die hard
Synonyms: hardly
hard (adv.)
indulging excessively;
Synonyms: heavily / intemperately
hard (adv.)
into a solid condition;
concrete that sets hard within a few hours
hard (adv.)
very near or close in space or time;
it stands hard by the railroad tracks
a strike followed hard upon the plant's opening
they were hard on his heels
hard (adv.)
with pain or distress or bitterness;
he took the rejection very hard
hard (adv.)
to the full extent possible; all the way;
hard alee
the ship went hard astern
swung the wheel hard left