A friend just sent me this fascinating look at the old English folk song, Scarborough Fair, rearranged, of course, by Simon & Garfunkle in the 60's. And there was some interesting word lore here. The background of the herb imagery is also especially intriguing.

"Scarborough warning" still means 'without any warning' in today's English.

http://www.geocities.com/paris/villa/3895/

(scroll down to "Explanation of the Lyrics," second paragraph, for the history of the phrase)