Corylus avellana (Betulaceae)

A deciduous, thicket-forming, multi-trunked, suckering shrub, it can reach a height of 4-6 m (12-20’). This hardy shrub is native to Europe, western Asia and northern Africa.  It carries separate male and female flowers on the same plant. The male flowers, pale yellow-gray, form drooping catkins, each up to 5-8 cm (2-3”) long. 
Hazelnuts, also known as filberts, appear in terminal clusters of one to four — often three — and are half covered in ragged husks. The husk around the nut extends beyond the nut by at least one inch to form a beak. Those nuts ripen in August-September, close to St. Philibert (August 20th) — hence the name filbert. As for hazel, it is Old English for a shrub. 
Count nine calories per nut. The Swiss hazelnut chocolate appeared at the turn of the twentieth century and has been a lasting commercial success. 
But where did the plant originate? My personal history here comes into play. I am French-born of Hungarian parents. Accordingly, my vocabulary in Hungarian is poor. I know, however, the word for hazelnut, mogyorô [mod’orō.]  This is not untypical knowledge for a child, of something not only edible, easily and frequently found on a long-domesticated plant, in-between a shrub and a tree. 
Before going on, a reminder on conventional knowledge about the Hungarian language. Originating in Central Asia, in the general area of the Gobi Desert, it is part of the Finno-Ougrian family of languages. Finnish is a related language. However, Finnish and Hungarian share very few words.
Let us now review critically the evidence on that example, the Hungarian name for hazelnut.  
As it turns out, this word flags an issue in both linguistics and botany. It is one of few words the Hungarian language has in common with Turkic languages, Chuvash in particular. The Chuvash people are a Turkic ethnic group, native to an area stretching from the Volga Region to Siberia. 
A mere look at Old Turkish loanwords in the Hungarian language convinces that the Magyars of the Ural region came into close contact with this Turkish people, the Chuvash, engaged in animal husbandry. Accordingly, the Magyars changed their mainly predatory way of life to the more dignified one of livestock breeding. (Beyond Chuvash, mogyorô the Hungarian name for hazelnut, if one is to believe the linguist Alfréd Tóth, goes back to the Sumerian language in which mudum is a fruit.) 
Speaking of, the present-day Hungarian word for fruit, gyümölcs [ɟy.mølʧ], is also a borrowing from Chuvash, during coexistence of the Magyars and the Chuvash in the same geographic area, 5th-9th centuries. So much for the radical uniqueness of the Hungarian language! So much for our laziness in embracing conventional knowledge without checking it! 
Coming back to hazelnuts, they were already cultivated by the Romans. Hazelnut appears to have been domesticated independently in three areas: the Mediterranean, Turkey, and Iran. An Easterly origin thus seems to be consistent with the linguistic evidence adduced here.