The word "merry-thought" is an old-fashioned term that refers to the forked bone in a bird's breast. This bone is also known as the wishbone, or clavicle. However, there are a few other words that could be used synonymously with merry-thought, such as furcula, which is a scientific term for the same bone, and furcaf, a Latin word that also means "forked bone". Additionally, the term "wishbone" is commonly used in everyday language, as well as the more poetic phrases such as "lucky bone" or "happiness bone". Regardless of the word used, holding onto the forked bone and making a wish is a timeless tradition that is still practiced today.