The "Bad Guy" singer, who is only 17, appeared on Jimmy Kimmel last month and was quizzed about the year 1984 when Fallon was age 17. After naming Madonna, who Eilish knows, Kimmel asked, "Can you name a Van Halen?"
"Who?" she replied.
The moment went viral weeks later with some music fans flabbergasted Eilish, who was born in 2001, didn't know the rock band. The Van Halen brothers, Eddie and Alex, formed the group eventually known as Van Halen with bassist Mark Stone and singer David Lee Roth in 1972. Van Halen was inducted into the Rock and Roll Hall of Fame in January 2007, when Eilish was 5 years old. Eddie Van Halen's son Wolf, who became the bassist for the band, told people to give her a break.
"Music is supposed to bring us together, not divide us," he tweeted Monday. "Listen to what you want and don’t shame others for not knowing what you like."
Rob Sheridan, the former art director for Nine Inch Nails, also weighed in.
Former Deadspin columnist Drew Magary quipped, "If you're surprised Billie Eilish has never heard of Van Halen, well then you might be a LOT more surprised by the s*** Eddie Van Halen himself is oblivious to." The tweet linked to a Billboard article where Eddie Van Halen said he wasn't familiar with the work of Radiohead, Metallica or Guns N' Roses because he doesn't listen to music.
Many others came to Eilish's defense, too.
Eilish is up for six Grammys in January and is the youngest artist to earn nominations in all four major categories – Album of the Year, Record of the Year, Song of the Year and Best New Artist.
Read more from Yahoo Entertainment:
Want daily pop culture news delivered to your inbox? Sign up here for Yahoo Entertainment & Lifestyle’s newsletter.