In 1928 the Indonesian nationalist movement chose it as the future nation's national language. Its name was changed to Bahasa Indonesia, literally: "the language (bahasa) of Indonesia". In English we call the language "Indonesian": it is not correct to call it simply "Bahasa".
The word "Bahasa" is often incorrectly used in English to refer to Indonesian, often by Western expatriates and English-speaking Indonesians. The question "Do you speak Bahasa?" literally means "Do you speak language?" When Indonesian or Malay speakers refer to other languages, the word "Bahasa" is used; for example, Arabic is called Bahasa Arab literally "Arab language".
Source:
http://en.m.wikipedia.org/wiki/Bahasa