Big tech companies including Meta and Microsoft already have intellectual property rights to the same letter and apparently it is so widely used Twitter could waste a fortune trying to defend the name in court.

Trademark attorney Josh Gerben said that there were nearly 900 active US trademark registrations that already cover the letter X in a wide range of industries.

"There's a 100% chance that Twitter is going to get sued over this by somebody," he said.

Musk renamed social media network Twitter as X on Monday and unveiled a new logo for the social media platform, a stylised black-and-white version of the letter. This X has started appearing on Android phones.

Microsoft since 2003 has owned an X trademark related to communications about its Xbox video-game system. Meta Platforms - whose Threads platform is a new Twitter rival - owns a federal trademark registered in 2019 covering a blue-and-white letter "X" for fields including software and social media.

Meta and Microsoft likely would not sue unless they feel threatened that Twitter's X encroaches on brand equity they built in the letter, Gerben said.