I grew up in Franklin Co. IL and went to school in Sesser. I have never heard of any O'Lomans in any of the surrounding counties. There are many Lomans that have been in the area since the 1850's and all directly related to my Loman family. They descended from William Loman/Lowman and Sally Golden both from the North Carolina/Kentucky area. Since Williams parentage has never been determind it is not known where the Loman/Lowman name originated. Here is what I can tell you, first there was no Sesser in 1892, so your great great grandfather coud not have been born there. Also there are no Loman's of O'Loman's listed in Franklin County, where Sesser is located in either 1880 or 1900. Of course the 1890 census was lost to fire so that can't be checked. There are several Lomans in Jefferson Co. IL which is just north of Franklin Co.
I have this info. from my family data which is very coincidental, this William J. is a first cousin to my grandfather.
WILLIAM J. LOMAN son of ISAAC BENJAMIN LOMAN and ELVIRA SEBELLE KIRK was born June 18, 1892, Elk Prairie Township, Jefferson County, Illinois, and died May 31, 1942, Mt. Vernon, Jefferson County, Illinois. He married (1) EMMALINE M. VANHORBEK daughter of EDWARD S. VANHORBEK and LENA F. BLYTHE. She was born Abt. 1892. He married (2) GRACE PAGE (Ukn.). She was born 1897, and died 1936.He married (3) GENEVIEVE DEPRIEST NOLEN (Ukn.).
Note for WILLIAM J. LOMAN: DEATH RECORDS JEFFERSON COUNTY ILLINOIS: LOMAN, WILLIAM J.; M/W; Y-49; 0000106; 1942-05-31; JEFFERSON; MT VERNON.
More About WILLIAM J. LOMAN: Burial: Masonic and Oddfellows Cemetery, Benton, Franklin County, Illinois
Children of WILLIAM J. LOMAN and EMMALINE M. VANHORBEK are: i. WILLIAM R. LOMAN.
ii. GLEN E. LOMAN b. Abt. 1912. (Listed in the 1920 census with his Van Horbeck grandparents in Jefferson Co. IL Listed in the 1930 census with his mother and a sister Caroline in Lake Co. IN.)
Children of WILLIAM LOMAN and GRACE PAGE are: iii. WILLIAM FLOYD LOMAN.