The Spanish word 'boina' meaning 'beret' traces back through Medieval Latin to Frankish origins. It comes from the Medieval Latin word 'abonnis', which meant 'woman's cap'. This in turn derived from the Frankish word 'obbunni', which meant 'tied on top', describing how these head coverings were secured. Over time, the word evolved both in form and meaning to specifically refer to the flat, round cap we know today as a beret.

The word 'boina' stands relatively independently in Spanish vocabulary, without many common related words. This is because it entered Spanish as a specific term for this type of headwear, and its specialized meaning has remained fairly constant.

While English doesn't have any direct cognates from the same Frankish root, it's interesting to note that the concept of the beret itself has been borrowed into English, though through French rather than Spanish channels. The English word 'bonnet', while not directly related to 'boina', similarly refers to a type of headwear and shows how different European languages developed their own terms for various head coverings.