Or search: taenia, cestoda, flatworm, echinococcus, platyhelminth
2 Syllables: SU
bellowed, echoed, fresco, frescoes, mellowed, narrowed, threshold
3 Syllables: USU
Francesco
4 Syllables: UUSU
manifesto

Found 9 words across 3 groupings. Skipped 1 excess word of a similar stem.