Heraldry
Heraldry is the science of designing or creating coats of arms. It also includes the use and regulation of arms.
Brief History on Coats of Arms
Originally, coats of arms were granted to individuals, not to families or surnames. They were used to identify individuals in battle. Later, the crown granted coats of arms to people who performed heroic deeds, made notable achievements, or who held prominent positions in society. The right to use a coat of arm was passed down to the male descendant.
Traditionally, most irish people didn't have coats of arms. But records granting coats of arms in Ireland date back to 1552 when a representative of the crown began keeping them. Edward VI, created the office of Ulster King of Arms in 1552. Most of the recipients were English and not Irish -- to those living in Ireland at the time. The Irish didn't believe in giving coats of arms by herald and so irish coats of arms were not common until the later part of the 17th century.
In the late 16 and early 17th century the Ulster King of Arms began visiting the landed gentry in Ireland. He asked for proof of their descent and drew up pedigrees for these families.
Sources on Heraldry
See Sir John Bernard Burke's book, "The General Amory of England, Scotland, Ireland and Wales: Comprising a Registry of Amorial Bearings from the Eariliest to the Present Time", last edition printed 1884. This book is available through the LDS Family History Center in book and film.
Records on Grants of Arms
Records of grants of arms are kept at the Genealogical Office in Dublin.