Douglas Harper's Etymology Dictionary
esclavage
chain or bead necklace worn by women and popular mid-18c., 1758, from French esclavage, literally "slavery" (16c.), from esclave (13c.) "slave" (see slave (n.)). So called from fancied resemblance to a slave's neck chains.
Wiktionary
esclavage
n. a type of chain or bead necklace.