The story
When someone attempts to register a Twitter account name that is already taken, the site suggests the inputted name followed by a long, randomly-generated string of numbers as an alternative (e.g. "@Wiktion74587432" instead of "@Wiktionary"). This has led to many anonymous accounts with handles that consist of a given name and a string of numbers (e.g. "@Jane74587432675").
Etymology from Wiktionary, CC BY-SA 4.0.