The Phethean surname, along with Vivian, Fython, Fithyan,Fiddian,Phythien Phythian etc is derived form the French Vivian, Vivien and Latin Vivianus; a derivative of vivus (“Living”), the name of a 5th -century martyr not uncommon in England from the 12th century. Its pronunciation and spelling are difficult and it appears in a variety of forms. There is much dialectical replacement of “f” and “v” cf Fivian and Fithian; also replacement of “th” and “d” cf Fidian. The initial “Ph” is probably just an artefact of transcription.
In addition “Surnames” (E. Weekley; John Murray 1917) states
“Frithu, peace, has given us many favourite font-names which have later become surnames, e.g. Domfrith (Dunsphrey, Dunpress), Frithugar (Fricker), Frithumund (Fiddyment) . To the last name, or to some other compound of Frithu, such as the once favourite Frithuswith or Friswid, patron saint of the University of Oxford, belong Fiddy, Fiddian, Phethean, Phythian. This element often becomes Free in modern surnames, e.g. Freestone from Frithustan, Freelove from Frithulaf It also appears via Old French in Frizzle, Froysell, which in Scotland has unaccountably become Frazer
