Or search: oddity, density, oddment, tenuity, rareness, nicknack, curiosity, showpiece, denseness, knickknack, scarceness, collectible, infrequency, peculiarity, collectable
3 Syllables: SUU
charities, charity, clarity, Hebrides, rarity, scarcity, verity
4 Syllables: USUU
asperity, austerity, celebrities, dexterity, hysterically, necessities, numerically, severities, severity, vulgarity
5 Syllables: UUSUU
insincerity, unreservedly
6 Syllables: UUUSUU
unpopularity

Found 20 words across 4 groupings.