Fred's hobby was collecting lyrics (in his lifetime he collected hundreds, including Roses of Picardy)

Fred Weatherley "collected lyrics" such as "Roses of Picardy" in the same sense any song writer "collects lyrics". There is a sense in which is true of anybody writing a song that becomes poopular - they've latched on to something in the air. But the songs aren't around to be sung before they put them together.