If ethnicity doesn't have to do with where you're from, then what it it? From dictionary.com
eth·nic (thnk)
adj.
1.
a. Of or relating to sizable groups of people sharing a common and distinctive racial, national, religious, linguistic, or b. cultural heritage.
c. Being a member of a particular ethnic group.
2. Of, relating to, or distinctive of members of such a group: ethnic restaurants; ethnic art.
Relating to a people not Christian or Jewish; heathen.
n.
A member of a particular ethnic group, especially one who maintains the language or customs of the group.