billberry = mustikka
Bilberry ( Vaccinium myrtillus ) is closely related to North American wild and cultivated blueberries and huckleberries. It is also known as: blaeberry, whortleberry, (ground) hurts, whinberry, winberry, windberry, wimberry, myrtle blueberry & fraughan. Source: Wikipedia
It can get confusing because in Northern Europe Blueberry, the close relative of Bilberry is also just called blueberry, or "bush blueberry". For example the Swedish name of Bilberry (blåbär) means Blueberry. The Finnish name (mustikka) for bilberry (and blueberry) means, loosely translated: "Blackie".
* see note in right column
blueberry / highbush blueberry = pensasmustikka (Swe: Amerikanskt blåbär)