Or search: sneak, covert, sneaky, stealthy, concealed, surreptitious
2 Syllables: SU
burnings, burnished, churches, churlish, courage, curses, Curtis, earnest, earnings, Ernest, flourish, furnish, girlish, merges, nourish, nurses, perches, Perkins, purges, purplish, purses, scourges, searches, service, skirmish, surfaced, surges, Turkish, turnings, urges, verses, worketh, workings, yearnings
3 Syllables: SUU
emerges
3 Syllables: USU
assertive, coercive, discourage, discursive, encourage, researches, reverses, subversive

Found 43 words across 3 groupings. Skipped 6 excess words of a similar stem.