Green’s Dictionary of Slang

jib n.2

[abbr. proper name Antoine Gibus, the Fr. inventor who patented the hat in 1837]

(UK society) an opera hat.

[UK]J. Ware Passing Eng. of the Victorian Era 160/1: Jib (Soc., 1848–80). Flat-folding, ‘chimney-pot’ hat, closed by springs set in centre of vertical ribs. Name from that of the French inventor ‘Gibus’.