[UN UN INTENSIFIES]

Deidara has a habit of ending his sentences with nasal-like grunts (…うん, …un), roughly translated as "yeah" or "hm".

Sources:
Orginal Song: J. Dash - Wop
Vocal: Deidara (デイダラ)
Anime: Naruto Shippuuden

You can also watch this video on YouTube: