The English word luxury has roots in the Latin luxus. Luxus means ‘abundance’ or “sumptuous enjoyment”. A luxury can be defined as an indulgence. It can be something that is particularly elegant, or sumptuous. Charles Hodgen has a nice article on Luxury here.
In the Latin luxuria meant sinful enjoyment. Originally in French, Italian, and Spanish the equivalent words meant ‘lust’, and originally in Old English in the 1300s had a related meaning.
Luxury received a gradually improved meaning over the centuries according to the Online etymology dictionary. Meaning “habit of indulgence in what is choice or costly” is from 1630s; that of “sumptuous surroundings” is from 1704; that of “something enjoyable or comfortable beyond life’s necessities” is from 1780. First used as an adjective 1930.
Today luxury means having the nicest things — the best, the most elegance, the most sumptuous.
Buyers enjoy Cadillacs because they are luxury automobiles — they offer luxury appointments, fine leather, wood grains, abundant power, smooth but capable chassis. But don’t feel bad if your desire for a new Cadillac seems to border on lust — blame the language for not giving you the right terms to describe your emotions.