hi! When you're wondering where a word comes from (i.e. it's "etymology"), check any good dictionary or a specialist etymology dictionary. There's a handy "Online Etymology Dictionary", which has this entry for Romania:

Eastern European nation, name taken officially in 1861 at the union of Wallachia and Moldavia, from Latin Romani "people from Rome," which was used to describe the descendants of colonists there from Roman times; see Roman + -ia. In early use often Rumania, or, from French, Roumania. Related: Romanian; Rumanian; Roumanian.

Here are some previous threads which may be of interest

• Did the Roman Empire ever reach as far as Romania?

• What is Romania's connection to the Romans?

• Why does Romania speak a Romance language but none of the rest of Eastern Europe does?

• How did the region that has developed into modern Romania develop a Romance based language and not a slavic one like Bulgaria?

• Is there an historic reason why Romanians consider themselves Latin but the bordering countries who also were part of the Roman Empire do not?

• How come Romania is often referred to as 'Rumania' in older texts?