Joy.
It’s been an English word since around year 1200, carrying then the same meaning it does now of “a feeling of pleasure and delight.” Our English word comes from the French joie, which comes in turn from the Latin gaudium.
That gau- root is common to many Indo-European languages, including Ancient Greek gaio, which means “I rejoice!” I love that the noun joy is so closely related to the proclamation of the feeling. It’s especially apropos this time of year, when we’re not just celebrating the joy of Christ’s arrival, but proclaiming it for all to see and hear.