harbinger
/ˈhɑːbɪndʒə(r)/noun
1- a person or thing that announces or signals the approach of another通报（…即将来到）者, 预告者：
witch hazels are the harbingers of spring.
金缕梅预示春天的来临。
1.1
- a forerunner of something先驱。
词源
Middle English: from Old French herbergere, from herbergier 'provide lodging for', from herberge 'lodging', from Old Saxon heriberga 'shelter for an army, lodging' （from heri'army' + a Germanic base meaning 'fortified place'）, related to harbour. The term originally denoted a person who provided lodging, later one who went ahead to find lodgings for an army or for a nobleman and his retinue, hence, a herald （mid 16th cent.）.