Or search: sap, dope, fool, herb, lame, naif, twit, booby, dummy, naive, ninny, ovate, stupe, twerp, twirp
2 Syllables: SU
cinder, dinner, drinker, finger, ginger, glimmer, hinder, injure, inner, insert, intern, inward, linear, linger, Minster, pincers, Pindar, printer, ringer, singer, sinner, Skinner, spinner, spinster, splinter, Springer, swimmer, Swinburne, thinker, thinner, timber, tincture, tinder, tinker, vineyard, Windsor, windward, winner, winter
3 Syllables: SUU
insecure, insular, integer, miniatures, similar, singular
3 Syllables: USU
beginner, midwinter, nonlinear, unhindered, uninjured, Westminster
4 Syllables: USUU
dissimilar, Peninsular

Found 53 words across 4 groupings. Skipped 30 excess words of a similar stem.