Cul-de-sac

Cul-de-sac is, as defined by our American Heritage College dictionary, "a dead-end street." It is also a "saclike cavity or tube open only at one end." This noun is French and the cul means bottom, the de means of and the sac means sack. So literally the bottom of a sack. This makes sense when used referring to the kind of road, since there is a kind of circular sack of road with one opening. 

The reason I love the word is that for the longest time when I was little I used to refer to culs-de-sac as "sackets." So when I finally started saying the correct name for them, I was so proud of myself, that I said the word over an over again. I have also just illustrated another reason why I love this word. The plural for cul-de-sac is culs-da-sac! The 's' is in the middle of the word and I think that is just snazzy!