What once passed for normal, becomes a rarity (think: Renault 12). Usage debases the value of language so while our words remain set on the page, the meanings attached to them drift off and new meanings, hunting for home, attach themselves. So it is that the world outside our head is unstable and shifting and the words inside our heads lose value like sweating gold coin in a sack or drachmas, lire and roubles in wallets.
This is getting very post-modern, isn´t it? The word for a fixed reference changes its meaning and the thing it refers to changes as well. It´s all relative now, kids.