Snobs and Chauffeurs

Words don't necessarily keep the same meaning. Simple descriptive words such as rain or water are clear and necessary enough to be unlikely to change. Other more complex words have often come on quite a journey since they were first coined:

chauffer (French) to heat; then meant the driver of an early steam-powered car; subsequently chauffeur

sine nobilitate (Latin) without nobility; originally referred to any member of the lower classes; then to somebody who despised their own class and aspired to membership of a higher one; thus snob

theriake (Greek) an antidote against a poisonous bite; came to mean the practice of giving medicine in sugar syrup to disguise its taste; thus treacle

Are there any others you can think of?

Long-winded Words

These are often compounds or known as portmanteau words such as;
abkurzungsverzeichnis (German) a list of abbreviations
koyukon neelk'etoak'ee k'eelek'eebedee'oane (Athapaskan, USA) Seven
der Hottentottenpotentatentantenattentater (German) the would-be assassin of the aunt of the Hottentot dignitary
Have you come across any others even longer perhaps!