Question: In what century did the term "vegetable" become associated with a plant grown for food?
About the article "Vegetable", section "Etymology".

Candidate passages:
The word "vegetable" was first recorded in English in the early 15th century from Old French, and was in origin applied to any plant.
This is still the sense of the adjective "vegetable" in biological context.
The word is taken from Medieval Latin "vegetabilis" "growing, flourishing" (i.e.
of a plant), a semantic change from a Late Latin meaning "to be enlivening, quickening", a derivation of the verb "vegetare" "enliven", which is derived from "vegetus" "to be alive, active" (related to "vigor"), in reference to the process of a plant growing.
In 1767, the meaning of the term "vegetable" was specified to mean "plant cultivated for food, edible herb or root."
The year 1955 noted the first use of the shortened, slang term "veggie".
As an adjective, the word "vegetable" is used in scientific and technical contexts with a different and much broader meaning, namely of "related to plants" in general, edible or not — as in "vegetable matter", "vegetable kingdom", "vegetable origin", etc.
The meaning of "vegetable" as "plant grown for food" was not established until the 18th century.
A vegetable garden (also known as a vegetable patch or vegetable plot) is a garden that exists to grow vegetables and other plants useful for human consumption, in contrast to a flower garden that exists for aesthetic purposes.
It is a small-scale form of vegetable growing.
A vegetable garden typically includes a compost heap, and several plots or divided areas of land, intended to grow one or two types of plant in each plot.
Plots may also be divided into rows with an assortment of vegetables grown in the different rows.
It is usually located to the rear of a property in the back garden or back yard.
Many families have home kitchen and vegetable gardens that they use to produce food.
In World War II, many people had a garden called a "victory garden" which provided food and thus freed resources for the war effort.
With worsening economic conditions and increased interest in organic and sustainable living, many people are turning to vegetable gardening as a supplement to their family's diet.
Food grown in the back yard consumes little if any fuel for shipping or maintenance, and the grower can be sure of what exactly was used to grow it.
Organic horticulture, or organic gardening, has become increasingly popular for the modern home gardener.
There are many types of vegetable gardens.
The potager, a garden in which vegetables, herbs and flowers are grown together, has become more popular than the more traditional rows or blocks. 
A vegetable oil is a triglyceride extracted from a plant.
Such oils have been part of human culture for millennia.
The term "vegetable oil" can be narrowly defined as referring only to substances that are liquid at room temperature, or broadly defined without regard to a substance's state of matter at a given temperature.
For this reason, vegetable oils that are solid at room temperature are sometimes called vegetable fats.
Vegetable oils are composed of triglycerides, as contrasted with waxes which lack glycerin in their structure.
Although many plant parts may yield oil, in commercial practice, oil is extracted primarily from seeds.
On food packaging, the term "vegetable oil" is often used in ingredients lists instead of specifying the exact plant being used. 
Jerusalem artichokes were first cultivated by the Native Americans long before the arrival of the Europeans; this extensive cultivation obscures the exact native range of the species.
The French explorer Samuel de Champlain found domestically grown plants at Cape Cod in 1605.
He then brought the plant back with him to France.
By the mid-1600s, the Jerusalem artichoke had become a very common vegetable for human consumption in Europe and the Americas and was also used for livestock feed in Europe and colonial America.
The French in particular were especially fond of the vegetable, which reached its peak popularity at the turn of the nineteenth century.
The Jerusalem artichoke was titled 'best soup vegetable' in the 2002 Nice Festival For The Heritage Of The French Cuisine. 
"Dioscorea opposita", "Chinese yam", is native to China.
The Chinese yam plant is somewhat smaller than the African, with the vines about 3 meters (10 feet) long.
It is tolerant to frost and can be grown in much cooler conditions than other yams.
It is now grown in China, Korea, and Japan.
It was introduced to Europe in the 19th century when the potato crop there was falling victim to disease, and is still grown in France for the Asian food market.
The tubers are harvested after about 6 months of growth.
Some are eaten right after harvesting and some are used as ingredients for other dishes, including noodles, and for traditional medicines (Kay 1987).