Oaths of fealty in Maryland have been around since the founding of the colony. Early on they seemed to have had more to do with acknowledging Lord Baltimore's claim to Maryland than anything else. (Virginians and the proprietors of Pennsylvania, not to mention local Indian tribes, disputed that title and many colonists probably wondered why they had to pay rent to Lord Baltimore twice a year when they took all the risks and he provided only such services as served his interests.)
Here is an oath from a later period, about 1717. Below the images are my transcriptions.
Oath Required of the Charles County Commissioners in 1717 (Land Records M2/26).
The Subscriber do truly and Sincerely acknowledge & profess, testify and declare in my Conscience before God and the world that our Sovereign Lord King George is Lawful and Rightful King of Great Britain and all other the Dominion and Countries thereto belonging, and I do Solemnly and Sincerely declare that I do believe in my Conscience that the person pretended to be the prince of Wales during the life of the Late King James and since his death pretending to be and taking upon himself the State and Title of King of England by the name of King James the third or of Scotland by the name of James the Eighth or the State and Titles of King of Great Britain hath not the Right or Title whatsoever to the Crown of the Realm of Great Britain or any other the dominions thereto belonging and I do renounce, Refute and Abjure any allegiance or obedience to him and I swear that I will bear faith and true allegiance to King George… .”
To this was added the following oath:
I Do Likewise declare that I believe there is not any Transubstantiation in the Sacrament of the Lords Supper or in the Elements of Bread and Wine at or before the Consecration thereof by any person whatsoever.
The first oath ties early 18th-century Maryland politics into those of Hanoverian Great Britain, specifically in regards to the Scottish Stuarts having lost the thrones of England and Scotland, and rule over all British dominions, to the Hanovers, beginning with King George I. The taking of political oaths is alive and well in the modern Western world. (Perhaps you have heard of the pledge of allegiance and other oaths taken upon the acceptance of a government job or application for a passport?) The second oath, however, is a religious test banned by the Bill of Rights in the US Constitution.
Transubstantiation is a integral part of Roman Catholic ritual, wherein the host and wine are turned into the body and blood of Christ. To reject this concept is to reject Catholicism. And, since the reigning British monarchs since King Henry VIII have also been the titular heads of the Church of England, to accept Catholicism was to reject the full authority of the monarch.
All of this makes perfect legal and procedural sense, but it still strikes me as a little bizarre to have County Commissioners--really just provincial farmers and lawyers--caught up in the political insecurities and religious bigotries of a distant mother country. Religious bigotries and particularly anti-Catholicism, however, permeated Colonial Maryland and persisted through the 19th century and, in some quarters, remain alive today.