When a vocalist scats what do they use for the words?

When vocalists sing scat, they replace the lyrics of a song with improvised vocables, syllables, or sounds that take the place of the vocals. These vocables are often nonsense or meaningless syllables that are used to create a unique rhythmic or melodic pattern. Scat singing can be a way for vocalists to add ornamentation or embellishment to a performance, showcase their vocal abilities, or simply create a more expressive vocal line.