These are two villages in Hertfordshire. Welwyn /ˈwelɪn/ is better known these days for Welwyn Garden City, founded by Ebenezer Howard, but somewhat later than Letchworth Garden City (the world’s first garden city), and which is situated a couple of miles away from the old Welwyn village. Willian /ˈwɪlɪən/ is in fact one of the three villages that make up Letchworth GC, the other two being Norton, and Letchworth itself.
Both names are derived, according to the English Place Name Society’s volume on Hertfordshire (1938), from the Anglo-Saxon word for “willow”, which occurs in the forms welig and wylig. The first of these gave rise to Welwyn, and the second to Willian (both come from the dative case of the word, so that its meaning is literally “at (or to) the willows”). Presumably welig and wylig are the forms in different dialects of Anglo-Saxon. The two villages are only about 10-15 miles apart, and yet seem to be on opposite sides of an isogloss. Is there anyone out there who can confirm the two dialects for me?
In case anyone has seen it, the recent movie “The World’s End” was shot mostly in Letchworth Garden City and Welwyn Garden City. Ironically, the film tells the story of a pub crawl, and Letchworth GC was the world’s original town with no pub: the first licensed premises in the town did not open until 1961, the town having been established in 1903 (Letchworth is also the site of Europe’s first roundabout – ca 1909 – it appears in the film).