It’s a DE9, not a DB9

https://www.osnews.com/story/142898/its-a-de9-not-a-db9/

Thom Holwerda Jul 25, 2025 · 1 min read
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You’ve seen them everywhere, especially on older computer equipment: the classic 9-pin serial connector. You probably know it as a DB9. It’s an iconic connector for makers, engineers, and anyone who’s ever used an RS232 serial device. Here’s a little secret, though: calling it a DB9 is technically wrong. The correct name is actually DE9.

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I honestly had no idea, and looking through the Wikipedia page, it seems this isn’t the only common misnomer when it comes to D-sub connectors.