The flic-flac is often performed as part of intermediate to advanced barre work.  It often functions as a connector step in barre work with a quick tempo, such as frappé or petit battement.  What are the origins of this term?  While most ballet words relate to their terminology through meaning, flic-flac relates movement to sound. 

Flic-flac pronounced [flik flæk] or fleek, flack.

In French, flic-flac is an onomatopoeia often used to represent the sound of the rain splashing onto the ground (think drip-drop, drip-drop), but it can also represent the sound of a whip, which ties in well with the motion of the flic-flac.

Turning en dedans, the dancer brushes the working foot in front of the supporting foot, crossing past 5th and stretching the foot, creating an over-crossed cou-de-pied as the supporting foot rises to demi-point.  The toes of the working foot brush the floor again as the body turns toward the barre and the working foot lifts to cou-de-pied derrière.  The turn can also be executed en dehors by first brushing behind the working leg, turning away from the barre, and finishing with the working foot in cou-de-pied devant.

You can certainly imagine the whipping action of the body as the dancer turns and also the whip of the leg as it brushed down and through fifth.  While flic-flac doesn't directly mean a whipping movement, it is the way the sound of the whip is represented orally and in writing.

In older texts, you may also find flic-flac representing the sound of a dancer's feet (remember that they were wearing healed shoes) during an entrance or while performing a step.  Before flic-flac came to represent a specific step, it meant only the click-clack of the dancers heels on the floor.