St Mary's Our Lady, Sidlesham - a speckled churchyard to the south?
The narrator on page 30 explains how Earwicker's agnomen is not derived from the Earwickers of Sidlesham in the Hundred of Manhood, but rather came about from a comment by the then King William IV that Humphrey was an earwig trapper as much a turnpiker.
Nonetheless, Joyce visited the graveyard at St Mary's Our Lady in Sidlesham, near Chichester in southern England, and had in his possession a guidebook stating that there could found at the church gravestones with curious names such as Earwicker, Gravy, Glue, Boniface, Anker and Northeast. (Peter Timmerman, 'The First Guide to Finnegans Wake', A Wake Newslitter, 16 (June, 1979) pp. 45-48).
While the fictional Earwicker was apparently not descended from the Sidlesham Earwickers, it is probable that Joyce's visit prompted him to use the name Earwicker in Finnegans Wake. He visited the church in 1923, prior to writing Chapter 2, the Here Comes Everybody chapter.
Several graves of Earwickers are present or at least still legible in the churchyard, the earliest being 1795, although no Glue's, Gravy's, Northeasts or Ankers were visible - except for the 'Glue' middle name of a Charles Glue Dibley on a World War One memorial (see picture below) which most likely harks back to a regional name. There was also a few legible Bonifaces. While no Earwickers are presently on the parish register, there were two Earwicker graves dated 1965, so it is feasible there is still a living descendent of Earwicker somewhere thereabouts.
William Earwicker d. 1795
Looks like Ann Boniface...
Charles Glue Dibley - 7th down, and Alfred Boniface Shrub - 2nd from bottom