Mayor of the Bull-ring
(Old Dublin). This official and his sheriffs were elected on May-day and St. Peter's Eve “to be captaine and gardian of the batchelers and the unwedded youth of the civitie.” For the year the Mayor of the Bull-ring had authority to punish those who frequented brotheis and houses of ill-fame. He was termed Mayor of the Bull-ring from an iron ring in the Corn Market, to which bulls for bull-baiting were tied, and if any bachelor happened to marry he was conducted by the Mayor and his followers to the market-place to kiss the bull-ring.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894