5 letter words:
brook11,
iroko9,
koori9,
4 letter words:
birk10,
boko10,
book10,
bork10,
brik10,
kobo10,
koro8,
rook8,
biro6,
boor6,
brio6,
broo6,
3 letter words:
bok9,
kob9,
irk7,
kir7,
koi7,
kor7,
oik7,
rok7,
bio5,
boi5,
boo5,
bor5,
bro5,
obi5,
obo5,
orb5,
rib5,
rob5,
oor3,
roo3,
2 letter words:
ki6,
ko6,
bi4,
bo4,
ob4,
io2,
oi2,
oo2,
or2,