This is also a line from the traditional British poem
Cold, Haily, Windy Night, which deals with a similar
scenario. The soldier begs a young lady to let him take shelter from the
elements, and she breaks down under repeated
pressure and "she opened and she let him in." Then she takes him into her bed and "she opened and she let him in." She blesses this night, and says "Soldier, soldier stay with me / Soldier, soldier won't you marry me?" But he bolts and leaves her to weep over her lost
maidenhead.
The poem was made into a song by
Steeleye Span on the album
Please to See the King. It's on the more
traditional end of their characteristic
Celtic boogie style.