In case you wondered about the last name - it is not a typographical error. From Wikimedia.
This redo of a van Dyck shows how a collar can become a bertha.
Keywords: van Dyck, Bone, Duchess, Feilding family, British, curly coiffure, jeweled ribbon headdress, square décolletage, chemise, modesty piece, three-quarter length under-sleeves, bertha, lace, elbow length puffed sleeves, basque bodice, basque waistline, full skirt, necklace, earrings, jeweled bodice ornament, bracelets, boa, fur