"Nosegay" is a homegrown word -- that is, it originated in English. Fifteenth-century Middle English speakers joined "nose" (which meant then what it does today) with "gay" (which at the time meant "ornament"). That makes "nosegay" an appropriate term for a bunch of flowers, which is indeed an ornament that appeals to the nose. Today the word "nosegay" is especially common in the bridal business, where it usually refers to a specific type of bouquet: a round, tight bunch of flowers as opposed to a cascading bouquet or other type of arrangement. Occasionally, the word is used metaphorically for things that somehow resemble a bouquet. For example, a compact collection of enjoyably lighthearted short stories might be called "a nosegay of a book."