It all begins innocently enough — a pretty miss catching a handsome fellow's attention. Fair enough, but there's more than meets the eye — a bit of trickery perhaps.
Sir Walter Scott was on to it, establishing pretty's reputation in alignment with the German prachtig, "a gallant alert fellow," as "one who was prompt and ready to act."
The pretty man came first, you see. Not just another pretty face, he became the possessor of wile, cunning, and mental agility, all of which contributed to his pretty wit.
Shakespeare's pretty made the word synonymous with both the "tricky" and the "attractiveness." This same usage continued into the 19th century, and by conveying substantiality, helped us fetch a pretty penny.
You've got to watch yourself with pretty. Historically, there's always been something contrived about her. She's well provided for when sitting pretty. Under the wrong circumstances, however, she's messy enough to create a pretty kettle of fish or land you in a pretty pickle.
A not so pretty colleague of hers is the word cute. It was originally acute, literally, "sharp at the end, coming to a sharp point, or pointed." Applied to people it made them "clever," "keen-witted," "sharp," or "shrewd." When acutely sick, your illness came on sharply to a point or crisis; making it severe or crucial.
Like so many words, over the years acute has also lost its edge, leaving it just somewhat cute. Everything nowadays is cute — an adjective reserved primarily for babies and sexy airheads of both sexes. There's nothing sharp about being cute today, though its overuse can leave one pretty sick; i.e. acutely ill.