The Same Person Commented On Their Own Answer Citing An Earlier (1932) Source That Already Made The Connection With Partial Derivatives - Blog Posts

<prev tags math mathblr one of the answers here claims plausibly that it's the 'd' in german 'Rand' the same person commented on their own answer citing an earlier (1932) source that already made the connection with partial derivatives so I'm not so sure it's a coincidence - the notation “𝕽∂” might've been working backwards from that