what is the origin of the word agriculture
It is a late Middle English adaptation of Latin "agricultūra", from "ager", "field", and "cultūra", "cultivation" or "growing".
Agriculture
The word "agriculture" is a late Middle English adaptation of Latin "agricultūra", from "ager", "field", and "cultūra", "cultivation" or "growing". 
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Agriculture [SEP] Etymology and scope
The word "agriculture" is a late Middle English adaptation of Latin "agricultūra", from "ager", "field", and "cultūra", "cultivation" or "growing". While agriculture usually refers to human activities, certain species of ant, termite and beetle have been cultivating crops for up to 60 million years. Agriculture is defined with varying scopes, in its broadest sense using natural resources to "produce commodities which maintain life, including food, fiber, forest products, horticultural crops, and their related services". Thus defined, it includes arable farming, horticulture, animal husbandry and forestry, but horticulture and forestry are in practice often excluded.