Folate was first isolated from spinach in 1941 and the scientists who purified this new vitamin decided to name it folic acid, from the Latin word for leaf, 'folium'. In 1943, other groups of researchers made the synthetic form which is now referred to as folic acid, which gets converted to the active folate in the body. Both are also known as Vitamin B9.
Folate and folic acid are not the same. Folate is what is found in nature and mainly in leafy vegetables. Folic acid is synthesized and is the form used in most supplements and for food fortification. It gets converted into folate in the body where it is active in many important biologic functions.