Europe
欧 centers on the idea of Europe, used in compounds for European things. The older meaning of 'vomit' or 'cough up' is rare in modern Japanese.
欧 originally combined 区 (a container) with 欠 (a person with an open mouth), suggesting vomiting or coughing up. In modern Japanese it is used almost exclusively as a phonetic abbreviation for Europe.
The left side 区 looks like a map of Europe with its distinct borders, and the right side 欠 looks like a person opening their mouth in awe at the continent's wonders.
For オウ, imagine a European person saying 'Oh!' in surprise: Oh -> オウ, as they discover the beauty of Europe.
Europe
Europe and the United States; Europe and America; the West
Northern Europe; Nordic countries; Scandinavia
Western Europe
Eastern Europe
Europe
Southern Europe
writing in a European language; European text; Roman letters
European-style; Western; Occidental
Japan Association for Trade with Russia & Central-Eastern Europe (ROTOBO)
Central and Eastern Europe
Central Europe
Asia and Europe; Eurasia
all Europe
Scandinavian design
Nordic person; Scandinavian; Northern European
Nordic Council
Stockholm school
Nordic Council
Norse mythology