Cape Annes is plural, agreeing with oilskins and boots. Haven't you ever worn one? See http://collections.ic.gc.ca/leach/songs/NFLD1/11-02.htm for the words to

The young composer, Art Scammel, was in high school when he wrote the song; his teachers would have whupped him for bad grammar. The DT has Anne minus an 'n.'