According to the dictionary at the Kamusi Project, tayari
is a Swahili word which means "ready" or "prepared":http://kamusiproject.org/en/lookup/sw?Word=tayari
That doesn't mean that Tayari is used as a name in the countries of East Africa where Swahili is an everyday language. There are a great many Swahili words which have been turned into names by African-Americans which are not used as names in Africa. And of course Tayari could have separate derivations from other languages. I can't find any reference to a sumo wrestler called Tayari, however.
You say your husband's father "apparently got the name from a local." Has your father-in-law himself told you this or did you get this secondhand? Family stories do sometimes get garbled in transmission.