The standard scholarly account of the cowrie oracle in English is William Bascom's Sixteen Cowries: Yoruba Divination from Africa to the New World, published by Indiana University Press in 1980. It is a large volume, much of it Yoruba text with facing English translation, and it sets Nigerian practice beside its New World descendants rather than treating either alone.
Two features of the book shape what a reference page can responsibly say. It was built from fieldwork, from what identifiable diviners were willing to say to a researcher at a particular time, so it is a record of specific practice rather than a canon. And it is comparative, which is why the atlas can state with confidence which of the sixteen parent names carry across from Ifa and which do not: that is exactly the kind of structural claim a comparison establishes.
Okana, the one-mouth throw, is documented within that record as the first of the sixteen parent signs.
What the same record does not establish, and does not attempt to, is a general meaning for any sign. Bascom collected material from people who chose what to give him, working inside a tradition that confers its interpretive knowledge through initiation. The proverbs, the myth narratives and the remedies attached to Okana belong to initiated diviners and to the person receiving a reading, and are not reproduced here.