The Word is Out: Espagnolette

Espagnolette [ih-span-yuh-let, ih-span-yuh-let]:

1. noun. (on a French window or door): one of a pair of rods, controlled by a knob mechanism, having hooked ends that engage in catches in the head and sill of the surrounding frame. A handle or knob is connected to a metal rod mounted to the surface of the frame, at about three or four feet above the floor. This type of lock is often used on a semi-trailer truck to fasten the rear doors. Espagnolette bolts can be identified by the use of a round bar, instead of a half-round bar used on a crémone bolt.
2. noun. Furniture. a feature, often a bronze mount, set at the top of a leg and having the form of a female breast or, more often, of a female figure with a stiff lace collar around the neck and under the chin; a small metal dome with a nipple used as an ornament (as on the top of a cabinet post) in French 18th century furniture making, esp. Regency and Rococco styles. Espagnolettes can also appear as a male or female masks. In whichever of the aforementioned forms they appear, they are usually applied to the sides or on the legs of a table or chair,  following the curve of the surface. 
3. noun. A French fabric, originally made of finely woven Merino wool.

Definition #3 above connects to #2 above by way of Gillot and his pupil, Jean-Antoine Watteau, who made fashionable the decorative motif of the stiff lace collar worn by Spanish women. It developed into a pattern used by furniture designers and is to be found on Regency writing tables and chests of drawers. The collar worn by Spanish women apparently is similar to a ruff,  which was donned in masquerade:

An example of definition #1 above:

An example of #2 above, on a German table:

Another example of #2:

Above pic from uniquefrance.com

Derivation: 

Espagnolette entered the English language 1865–70, from French, specifically from Provençal espagnouleto, diminutive of espanhol, meaning 'Spanish' or 'Spaniard'. From French Latin Hispania Spain + -olus -ole. It literally means a little Spanish female.

The derivation clearly shows that whichever definition of espagnolette we are dealing with, it originated in Spain. To connect the two senses of the word espagnolette together, the stiff high collar/ornamental figure motif on furniture, with the door and window locking mechanism is, well, conjectural on my part, however I am speculating that the link between the two might be the 'collars' top and bottom of the door mechanism, which the espagnolette bolt (the 'neck', so to speak) is tightly fitted.