This can be seen in the American West with adoption of Spanish words, through the use of pidgins and other trading languages, and in the adoption of words from India and other areas of the British Empire. Often a foreign word expresses an idea or a nuance better than existing words. Nouns are frequently adopted for this reason, but not all such words are nouns. Words and phrases such as lassez-faire express ideas that couldn't be easily expressed without adopting the words into English. Often people use foreign words to show a sophistication and worldliness.
Foriegn words can be a status symbol.
Also, certain technical disciplines follow a practice of adopting words from Latin or Greek, because these were once the languages of educated people. This is the coining of a new word. This process is relatively rare compared to the number of roots from inheritance or borrowing. There are basically two types of root creation, motivated and ex nihilo . One fairly common form of motivated root creation is echoic or onomatopoetic words.