Because Spicy Chicken's hit song is called Anaconda. According to the query Sina Entertainment Network shows.

1, Spicy Chicken's original name Nicki Minaj's hottest song in China is called "Anaconda", so Anaconda became Spicy Chicken's nickname.

2, Nicki Minaj, born December 8, 1982 in Trinidad and Tobago*** and the country of St. James, is an American female rap singer and songwriter.