Fa-sullī is a feminine singular imperative from salla, yasullu, “to pull out or draw away.” Thiyābī (“my garments”) is the object, while min thiyābiki evokes removal from among “your garments.”
The literal picture is of two sets of garments becoming disentangled. The poet transfers this material image to emotional intimacy and the separation of two people. Traditional interpretation also connects the garments with the heart’s attachment: if the relationship is unwelcome, let it be severed.
Tansul expresses the resulting withdrawal. Fa-sullī gives the action, and tansul the separation that follows, both parts of a single image.