I kindly disagree with your idea that Gaddy / Geddy / Gaddie / Geddie are different names. I find it unlikely that the clerk's intended to distinguish between last names. Such as the following example of James Gaddie/Geddie: These Clerks were not in any way good spellers from what I can surmise.
Patricia Gaddie of the Geddie/Gaddie Clan
BAPTISMAL RECORDS - OLD BLUFF PRESBYTERIAN CHURCH Cumberland County, North Carolina 1816 April 28th - Daniel McPhail Gaddi baptized son of …………….
1817 August 30th - Then was baptized Donald Gaddie son of John Gaddie and his wife Anny Gaddie
1819 November 28th, Christian Gaddie daughter of John Gaddie and his wife Anny
1822 November 10th - Alexr Gaddie infant of Alexr Gaddie and his wife Anny
1787 Jan 7th [abt] - Mr. James Gaddy and his spouse Chatrin McFaile had a daughter baptized named Maragrat
1797 April 9 - James Gadie & Cathrin MacPhaile had a daughter baptized named Sarah
1821 October 28 - Then was baptized Dugald Gadie infant of John Gadie and his wife Anny
July 18th 1802 - James Geddie and his spouse Jennat Maxwel had a son baptized named John
1800 October 5th [abt] - James Geddy and his spouse Gennat Maxwell had a son baptized named Thomas
1795 January 4 - James Gedie & his spouse Cathrine McPhaile had a son baptized named Dugald