Ugg boots, the furry sheepskin boots that defined the 2000s, are apparently back with great interest and Gen Z cachet, according to data from the shopping website Lyst.

The site’s annual quarterly report, which highlights the “hottest” 20 fashion brands, was released Thursday and, as Insider noticedUgg is on it for the first time since the start of the index in 2017.

“Gen Z shoppers are reviving once-dormant brands…with more than 1.2 billion mentions on TikTok – Ugg’s influence is undeniable,” the report notes.

The boots also sold out during the holiday season, it added.

Generation Z, or born people between 1997 and 2012has shown a penchant for bringing back old technology and trends, from flip phones Unpleasant “vintagecorded headphones.

But Ugg boots go back much further – the word “ugg” is actually a generic term in Australia meaning boots made of sheepskin and fleece, according to the BBC.

The company that made the “UGG” boot, Deckers Outdoor Corporation, is based in the US and tried to trademark the word in Australia (where a court ruled that it was a generic word and therefore could not be trademarked), but the company added.

Company say the boots began to gain popularity in California in the 1980s. They were first featured on Oprah’s Favorite Things in 2000 (a huge brand maker at the time) and became “treasured commodities” at the start of the decade Fashion.

The boots later regained prominence with a fashion movement that prioritized “ugly” clothing, and have since become an unironically Gen Z favorite, per Insider. Kylie Jenner was too spotted wear them in November.