der Anpfiff
kickoff
The referee's whistle signal that indicates the start of a game, especially in soccer.
Kurz nach dem Anpfiff fiel bereits das erste Tor.
The first goal was scored shortly after kickoff.

kickoff / telling-off
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kickoff
The referee's whistle signal that indicates the start of a game, especially in soccer.
Kurz nach dem Anpfiff fiel bereits das erste Tor.
The first goal was scored shortly after kickoff.

'Der Anpfiff' is derived from the separable verb 'anpfeifen'. This verb can mean both 'to start a game with a whistle' and, colloquially, 'to reprimand someone', which explains both meanings of the noun.
Der Schiedsrichter pfiff das Spiel pünktlich an.
The referee kicked off the game on time.
You can recognize the difference between the meanings from the context. In a sports context (game, referee, stadium), it refers to the start of the game. If a person gets an 'Anpfiff' (telling-off) from another person, it means a reprimand.
Alle Spieler waren pünktlich zum Anpfiff auf dem Feld.
All the players were on the field on time for kickoff.
In a sports context, 'Anpfiff' (kickoff) is often used with time expressions such as 'kurz vor dem Anpfiff' (shortly before kickoff) or 'direkt nach dem Anpfiff' (right after kickoff). A typical verb is 'ertönen' (to sound): Der Anpfiff ertönt.
Die Fans warteten gespannt auf den Anpfiff.
The fans waited excitedly for kickoff.
In the meaning 'Tadel' (reprimand), the word is colloquial. It is often used with verbs such as 'bekommen' (to get), 'kriegen' (to get), or 'sich abholen' (to collect/get for oneself).
Für den Fehler hat er sich vom Projektleiter einen gewaltigen Anpfiff abgeholt.
For the mistake, he got a huge telling-off from the project manager.
impetus / kickoff / offense
'der Anstoß' and 'der Anpfiff' both belong to the beginning of a soccer match. But they do not mean the same thing. 'Anpfiff' is the referee's whistle signal. It indicates that the game may now begin. 'Anstoß' is the first kick of the ball after this signal. The words can easily be confused because both happen right at the start of the game. In practical terms, you can say: First comes the 'Anpfiff', then the 'Anstoß' follows.

Kurz vor dem Anpfiff wurden die Fans im Stadion noch lauter.
Shortly before kickoff, the fans in the stadium got even louder.
Beim Anstoß stand der Stürmer schon bereit am Mittelkreis.
At the kickoff, the striker was already waiting in the center circle.