To cosset someone is to look after them very softly — keeping them warm, comfortable, and protected from anything difficult. The word almost always carries a small criticism inside it. When a writer says a child was cosseted, they usually mean the child was protected so much that they never learned to cope. So it sits close to 'spoil', but where 'spoil' suggests giving too many things, 'cosset' suggests giving too much softness and shelter. It is a formal, bookish word — you will read it far more than you will hear it. Newspapers like it for complaining about people who have had an easy life: 'cosseted politicians', 'a cosseted upbringing'. The past participle 'cosseted' used as an adjective is by far the most common form. Occasionally it is used warmly, with no criticism at all, especially about comfort you pay for — a hotel might promise to cosset its guests, meaning to pamper them. The old noun 'cosset' meant a lamb that lost its mother and was raised by hand in the house; once you know that, the modern meaning makes immediate sense.

嬌慣、寵溺、呵護備至（多半帶有「保護過頭」的貶意，不是單純的疼愛）