There are many historical terms for these #PKM tools. Second brain is one of the worst and is primarily a marketing term. See: https://boffosocko.com/2021/07/03/differentiating-online-variations-of-the-commonplace-book-digital-gardens-wikis-zettlekasten-waste-books-florilegia-and-second-brains/#Second%20brain A smidgen of its use stems from the mistranslation of some Luhmann work which is better read as “secondary memory”. One of my favorites is Eminem’s “stacking ammo“.