There is an adjective in English language that sounded me until very recently very authentic and firmly. It has definitely a positive connotation. The ground meaning of the present concerned adjective "sheltered" is "1. protected or sheltered from storms, missile, etc. by wall, roof, border, or the like; 2. protected from the troubles, annoyances, sordidness,etc. encountered in competitive situation; 3. (of a business or industry) enjoying noncompetitive conditions, as because of a protective tariff.
Recently I learned in surprise that the adjective "sheltered" has in addition a negative connotation.
Saying someone is "sheltered" is generally a bad thing to say about him or her. It implies a lack of wisdom and experience. Most parents who shelter their children do so unnecessary they are just afraid to let them grow up.
There is a hint about "overprotected".
Would you share your personal opinion? Do you approve that irresistibly drawing to the slang?
I don't see it as a slang usage; we have talked about a child having a 'sheltered upbringing' for a long time and not only in slang contexts. The usage may have increased because the degree of protection offered nowadays in greater than before.