4 letters:
baba, baca, bada, baka, caba, cada, data, gaba, paca, papa, tada, tata

5 letters:
bab a, bacau, bacca, bad a, bag a, batta, bat a, bob a, bocca, bog a, bop a, botta, caaba, cab a, cad a, cappa, cap a, cata-, cat a, cod a, cop a, cotta, cot a, dabah, dab a, dacca, dad a, dagga, datta, dat a, da ca, dhaka, doc a, dot a, gabba, gab a, gad a, gag a, gappa, gap a, gat a, ghada, god a, gogga, gotta, got a, kaaba, kappa, kata-, kat a, koppa, padda, pad a, pappa, patka, pat a, pa ca, pod a, poppa, pop a, pot a, tab a, tacca, tad a, tag a, tak a, tappa, tap a, tatta, tat a, tod a, topau, top a, tot a

6 letters:
bach a, back a, baht a, cobb a, dock a, gaba a, gatt a, gott a, pack a, papa a, tack a, tac ca, todd a

7 letters:
captcha, gotta a

8 letters:
bought a, caught a, poppadom