Tiza - Upper West Region. Tiza is a small village halfway between Lawra and Jirapa. The name is derived from two Dagaare words - Te, meaning We, and zaa, meaning all. The story, which I was told a long time ago, is that a group of people looking for a place to settle decided that the area was acceptable to "all of us", "te zaa" in Dagaare.
I am trying to locate these places in Ghana Eastern Region, they are I understand to be fairly closely related settlements, for which no amount of online word or map search seems to show any results: 1. Osuruwasi (alternative spellings Osuruasi or Osuruase) and 2. Osuwasi (alternative spelling Osuwase)
The closest toponym I have to those in your enquiry is Osorase, which is indeed in the Eastern Region just south of Akim Oda, as shown here:http://www.indexmundi.com/z/?lat=5.845784&lon=-0.968036&t=p&r=20&p=Osorase&cc=gh&c=ghana%20%28GNS%20data%29 It is possible that the two place names you mention both come from a single source, as it is not uncommon to find twin names for neighbouring settlements in Ghana, often identified as - No.1 & - No.2.