3. Ken's pink sash in his ensemble replaces a waistcoat in a 3-part tuxedo - but more interestingly, it hails back to a protective and practical garment worn by military, sportsmen, and ushers alike.
The etymology and history of the cummerbund is one of my favorites. The name comes from two Hindi words: kamar, meaning "waist", and band meaning "belt" or "tie". So cummerbund literally means a binder for the waist.
Cummerbunds were used in the Middle East and India for over 400 years, worn by military (likely used for the same purpose as kidney belts or cavalry belts), and some modern military groups still wear a cummerbund as part of their formal dress.
Cummerbunds were also used in sporting events in the 1800s and early 1900s, whether to wick away sweat or to provide postural support, perhaps in the same way as modern lifting belts.
Lastly, cummerbunds were often worn by servicemen in "fancy buildings", e.g. ushers in opera houses, doorkeeps in galas, bellhops in high-end hotels, etc. The upward-facing pleats of the belt functioned as several tiers of shallow pockets - enabling the wearer to keep ticket stubs, cash tips/change, or other small items within easy reach.
Depending on how tightly a traditional cummerbund is fitted to the body, it can also pull in the abdomen and prevent a spreading figure from outgrowing a single-size uniform.
These days, cummerbunds usually have an elastic or velcro backing and don't provide much support, but are now only for show. They're most commonly worn during proms or weddings as an alternative to a waistcoat - so it's more lightweight and cool for someone who doesn't want too many layers.