'Unknown' was apparently a musical instrument maker. According to his great-great-grandson George Butler, he was from Co. Kilkenny where he was apprenticed to a "shop" (I believe George meant a musical instrument making business here). His masters appear to have been anti-Catholic as George heard it said that his Kilkenny ancestor kept a catechism book hidden behind a brick in a wall. The story goes that 'unknown' left his job owing to ill treatment and made his way to Dublin where he continued (or started up) his trade. The family thinks he may have set up in business on Lower Exchange St., near the former Ss Michael & John church. A newspaper advertisement from the 1920s or 1930s found in a family scrapbook (name of newspaper and exact date unknown) appears to support the family's account that 'unknown' was indeed a musical instrument maker:
(Successor to G. BUTLER & SONS)
Being the 5th generation in direct line trading in Dublin since the rebellion of 1798.
The "J. Butler" mentioned could only have been Jennie Butler, a great-great-granddaughter of 'unknown', indicating that 'unknown' was the first generation to run the business in Dublin. However, newspaper advertisements from the 1870s state that the business was "originally established in Dublin in the year 1826". This ties in with William Waterhouse's 'The New Langwill Index: A Dictionary of Musical Wind-Instrument Makers and Inventors' (London, T. Bingham, 1993) which tells us that the business was founded by George Butler in 1926. Even if 'unknown's name was George it is unlikely that it was he who founded the business as he would have been in his fifties or sixties in 1926. Perhaps 'unknown' was indeed involved in the manufacture of musical instruments but it appears it was his son George who was the first family member to own his own business.
The Butler surname is Norman in origin and used to mean 'wine steward'. The name has the same root as the modern French "bouteille" meaning 'bottle'. The name was then extended to denote the chief servant of a household and, in the households of royalty and the most powerful nobility, a high-ranking officer concerned only nominally with the supply of wine. In Ireland most of the Butlers are descended from Theobald Fitzwalter, brother of the Archbishop of Canterbury, who was created Chief Butler of Ireland by Henry II in 1177. The huge territories he was granted were mainly in counties Tipperary, Limerick and Wicklow.