Coffee is indigenous to the highlands of Ethiopia/Eritrea and was introduced from there to the Yemen quite late, I think in the 17th century. The Arabic name bunn is borrowed from Tigre or Tigrinna. In Yemen people still say bunn for "coffee" (the drink), but elsewhere in Arabic it is used only for the berry. Coffee was introduced from Yemen to Istanbul and from there to Europe. The Dutch indentified (by folk etymology) the native name bunn with the Dutch word for "bean", hence our usage "coffee bean". Coffee is of course not made of beans but of berries.