What are some of your favorite words that are being used less and less? A few of mine are:

jet set

(JD) juvenile delinquent

hullabaloo

neurotic

next-of-kin

swamp cooler

playpen

rumpus room

the military-industrial complex

fuss-budget

the ecology movement

third-world

katywampus

nonplussed

mortified

pacification

gilded

Source: https://www.slideshare.net/nielrich013/stylistics-26050112