To one of the the original questions: "I steal unto her shieling lorn / And thru the dorring peep" ... A shieling is an outbuilding where sheep are kept over winter. I had always thought that it was "Shieling lawn" but will stand corrected. Regardless of this he is hiding behind the sheiling, trying to catch a glance of her through the open doorway. Presumably, as noted by the cricket's singing, it is summer and thus allowing for an open door rather than peeping through the window which would be far less acceptable in any song.
Moira asked: "Is he a peeping tom?" The short answer, to me, would be yes. I always think of this as a "Stalking song".
However, the passion and longing in this piece, bears no ill intention and is to my mind the "Unchained Melody" of traditional folk.
Jeany Redpath's rendition is perfect to my ear and her ornamentation, flawless.