{orko} is glossed as "orc" or "orch" (the latter spelling is from Sindarin).
{orka} means a kind of cetacean. The two words differ only in the final vowel,
which means that if they are rafsi fu'ivla, then they collide. Are they rafsi
fu'ivla? I don't remember about words that begin with a vowel, except that if
a rafsi is put before them, an apostrophe is inserted as an interfix, e.g.
{miky'enri}.