The word "coo" is a verb that typically refers to the soft, murmuring sound made by doves and pigeons. It can also describe a gentle or affectionate way of speaking, often used when addressing someone in a tender manner. For example, someone might "coo" to a baby or loved one to express warmth and fondness.
The word "coo" is thought to have originated in the early 15th century, likely imitative of the sound made by doves and pigeons. It may derive from the echoic representation of the sound, resembling the way these birds communicate.