The word grit has been in the language since Old English times. It derives from a verb meaning “to crush or to grind.”
Both the noun and the adjective have literal and figurative uses. I’ll give the literal definitions first.
grit noun: Minute particles of stone or sand, as produced by attrition or disintegration.
gritty adjective: Containing, consisting of, or full of grit; sandy.
As a verb, grit has the following meanings:
to emit a grinding sound
to spread or cover with grit
to cause the teeth to grind or grate
Note: Speakers agreeing to something against their will are said to speak “through gritted teeth.”
Grit has industrial uses. Sandpaper is graded according to grit ranging from coarse to fine. Grit can be added to a final sealer coat to increase the coefficient of friction. Some kinds of grit are fed to caged birds as an aid to digestion.
Unwanted grit is another matter:
I noticed yesterday at lunchtime that I had a piece of grit in my eye under the lid.
We live in the desert and our bread contains a lot of grit.
Walking barefoot on hot or gritty surfaces for extended periods can cause foot blisters.
The figurative use of grit to mean, “firmness or solidity of character,” originated as nineteenth-century US slang. The novel True Grit takes its title from this sense of the word. In the movie, Colonel Stonehill asks Mattie Ross why she chose Rooster Cogburn to help her find her father’s killer:
Col. Stonehill: Do you entertain plans of ever leaving this city?
Mattie Ross: Yes, I’m off early tomorrow morning for the Indian nation. Marshal Rooster Cogburn and I are going after the murderer, Tom Chaney.
Col. Stonehill: Cogburn. How did you light on that greasy vagabond?
Mattie Ross: They say he has grit. I wanted a man with grit.
The most common figurative meaning of gritty is, “harsh; bleak; unsparingly realistic”:
Before Sam Spade, Hammett earned fame for his gritty detective fiction featuring the Continental Op, a nameless private detective in San Francisco.
Some video games have been portrayed in a film noir style, using heavy, gritty, dirty urban themes.
It [the Hudson Yards area] was once a gritty stretch of Manhattan known for rail yards, warehouses and aging industrial buildings, so desolate it was dubbed ‘The Wild, Wild West’.
Thanks to a book by educational researcher Angela Duckworth, grit has become a buzzword in the education establishment. In her book, titled Grit, the word is defined as “the quality that enables individuals to work hard and stick to their long-term passions and goals.” Courses and techniques are being developed to “teach grit.” In this context, the adjective gritty is used to mean, “having grit.”
When I was a child, grown-ups referred to such qualities with words like character and gumption, defined as follows:
character noun: The sum of the moral and mental qualities which distinguish an individual.
gumption noun: initiative, resolution, and effort.
In those days, “teaching grit” at school would have been seen as ridiculous. Children with parents like the ones in my extended family had a start on grit before they ever got to school.