Both songs were inspired from an old tradition English folk ballad, “Scarborough Fair.” I find it interesting that Dylan (in 1962) and Simon (in 1965) each learned the original ballad from the same person, Martin Carthy, an English folksinger <http://en.wikipedia.org/wiki/Martin_Carthy>. One important difference, however, is the fact that Dylan used the ballad to create something new (typical of folksingers). Being a folky himself and having learned the ballad from Carthy a few years after Dylan, Simon was undoubtedly cognizant of the fact that the ballad had inspired Dylan’s “Girl from the North County.” I wonder if this is why Simon decided to stick close to the original ballad. Whatever the reason, I am thankful–Simon and Garfunkel created a masterpiece by staying true to the ballad.
Wikipedia has a good synopsis of the origins of the original ballad as well as its impact on Dylan (in 1962) and Simon (in 1965). Here are some highlights from Wikipedia:
Dylan (from <http://en.wikipedia.org/wiki/Girl_from_the_North_Country>):
The song was written following his first trip to England in December, 1962, upon what he thought to be the completion of his second album. It is debated as to whom this song is a tribute to, some claim former girlfriend, Echo Helstrom, and some Bonnie Beecher, both of whom Dylan knew before leaving for New York. However, it is suspected that this song could have been inspired by his then girlfriend, Suze Rotolo. Dylan left England for Italy to search for Suze, whose continuation of studies there had caused a serious rift in their relationship. Unbeknownst to Dylan, Rotolo had already returned to the United States, leaving about the same time that Dylan arrived in Italy. It was here that he finished the song, ostensibly inspired by the apparent end of his relationship with Rotolo. Upon his return to New York in mid-January, he convinced Rotolo to get back together, and to move back into his apartment on 4th Street. Suze Rotolo is the woman featured on the album cover, walking arm in arm with Dylan down Jones Street, not far from their apartment.
While in London, Dylan met several figures in the local folk scene, including English folksinger Martin Carthy. “I ran into some people in England who really knew those [traditional English] songs,” Dylan recalled in 1984. “Martin Carthy, another guy named [Bob] Davenport. Martin Carthy’s incredible. I learned a lot of stuff from Martin.” Carthy exposed Dylan to a repertoire of traditional English ballads, including Carthy’s own arrangement of “Scarborough Fair,” which Dylan drew upon for aspects of the melody and lyrics of “Girl from the North Country,” including the line from the refrain “Remember me to one who lives there, she once was a true love of mine”. Musically, this song is nearly identical to his composition “Boots of Spanish Leather”, composed and recorded one year later for the album The Times They Are a-Changin’.
Simon (from <http://en.wikipedia.org/wiki/Scarborough_Fair_(ballad)>):
Paul Simon learned the song in London in 1965 from Martin Carthy, who had picked up the tune from the songbook by Ewan MacColl and Peggy Seeger. Art Garfunkel then set it in counterpoint with “Canticle”, a reworking of Simon’s 1963 song “The Side of a Hill” with new, anti-war lyrics. It was the lead track of the 1966 album Parsley, Sage, Rosemary and Thyme, and was released as a single after being featured on the soundtrack to The Graduate in 1968. The copyright credited only Simon and Garfunkel as the authors, causing ill-feeling on the part of Carthy, who felt the “traditional” source should have been credited. This rift remained until Simon invited Carthy to duet the song with him at a London concert in 2000. Simon performed this song with The Muppets when he guest starred on The Muppet Show.
Before Simon had learnt the song, Bob Dylan had borrowed the melody and several lines from Carthy’s arrangement to create his song, “Girl from the North Country”, which appeared on The Freewheelin’ Bob Dylan (1963), Nashville Skyline (1969) (together with Johnny Cash), Real Live (1984) and The 30th Anniversary Concert Celebration (1993).
As for your question about Parsley, Sage, Rosemary and Thyme, Wikipedia again has some interesting material (<http://en.wikipedia.org/wiki/Scarborough_Fair_(ballad)>):
Parsley has been used as a digestant, which should take the bitterness out of certain comestibles. Some medieval physicians used this herb in a spiritual manner.
Sage is renowned as a symbol of power.
Rosemary represents fidelity, love, and remembrance and is therefore often used in traditional wedding customs. Rosemary for remembrance.
Thyme symbolizes courage and thus found its way into heraldry.
Another interpretation is that the four herbs are being used in charms to ward off the evil eye.