In literature, "Oxfordian" is the name of the theory attributing the authorship of William Shakespeare's
works to Edward de Vere, 17th Earl of Oxford (1550-1604) and also the name given to a person who believes in this theory. ("Stratfordian" is used to describe a person who believes Shakespeare himself to be the true author, since Shakespeare was from Stratford-upon-Avon.) The Shakespeare Oxford Society, an organization founded in 1957 and dedicated to promoting de Vere as the true author of the works attributed to Shakespeare, calls their annual scholarly publication The Oxfordian.
In short, Oxfordians claim that William Shakespeare did not have the education or court connections to write things depicted in the plays, and that he was not recognized as their author during the period when the plays were first performed. Of the several other names that have been put forth as possible authors, they feel that Edward de Vere's life has many incidents that are reflected in the works of Shakespeare and that de Vere was known as a court poet who wrote under pseudonyms.
In geology and paleontology, "Oxfordian" refers to a sub-division of the late Jurassic period. This term also originates in reference to the English county of Oxford where strata from this period were excavated early in the study of fossils; a 1911 encyclopedia says "the term Oxfordian was introduced by d'Orbigny in 1844."