A brand of nursing and medical scrubs; likely a reference to the hospital visit ('You came in to the ER') mentioned later in the song. The poetic function of the reference seems to lie in its juxtaposition with the Nicks-esque "long black shawl" in the previous line.
This line also references, albeit inaccurately, the first few lines of the Stevie Nicks hit, Edge of Seventeen, wherein Nicks sings "Just like the white-winged dove sings a song..."
See Also: seventeen
from Stevie Nix