Migration patterns of Neely/Neeley/Neelly/Neelley/Neily/Neilly/Nealy . . . the list goes on.

I am interested primarily in my immigrant ancestor Thomas Neely ( b. between 1776 and 1790) who was most likely born in Scotland (per 1880 census of his son's family) but immigrated to the Americas before 1819 and married a Yorkshire woman. The city directory of Cincinnati, where his son is born says England. The surname Neely indicates Ireland. I am wondering about what thr most likely Journey for him would have been. What would have taken Thomas' parents to Scotland from their native Ireland? I don't have verification of his marriage so it may be possible he married in England then came to the U.S.