Portmanteau (luggage)
A portmanteau is a piece of luggage, usually made of leather and opening into two equal parts. Some are large, upright, and hinged at the back and enable hanging up clothes in one half, while others are much smaller bags (such as Gladstone bags) with two equally sized compartments. The word derives from the French word portemanteau (from porter, "to carry", and manteau, "coat") which nowadays means a coat rack but was in the past also used to refer to a traveling case or bag for clothes. Portmanteau mail bag

In the 1700s the term would also have described a Mail bag. This continued in the 1800s for bags used by the Post Office. An 1823  resolution in Congress further stated that "locks...will be placed on the portmanteaus containing the principal mails (which) can only be opened...at the distributing offices." References

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Luggage