"Word fossils" are words that we don't really use anymore, except as part of an idiom or expression: "What in 𝙩𝙖𝙧𝙣𝙖𝙩𝙞𝙤𝙣?!" "Good 𝙧𝙞𝙙𝙙𝙖𝙣𝙘𝙚!" & "Moral 𝙩𝙪𝙧𝙥𝙞𝙩𝙪𝙙𝙚." But how do words become "fossilized" & how long does it take?