Re-Venn-ge of the Connecting Wall

^{An entry in Fortnightly Topic Challenge #42: Wordless Connecting Walls}

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Today I created a connect-wall puzzle (for which a solver would need to partition 16 items into 4 connected groups of 4, and then identify a 17th item that satisfies all four connections), but – would you believe it?! – I’ve forgotten all of the items in it! I have a hazy recollection of the connections behind the four groups, and I’ve found this helpful four-way Venn diagram that I made as an aid to constructing the puzzle… but I’m stumped!

Can you help me?

^{Colourblind-friendly version available here.}

Clues to the 4 categories:

1. One of the connecting categories relates to board-games – one game in particular, in fact…
2. Another category relates to web development.
3. Yet another category relates to history… or is it geography… Hang on, maybe mathematics? Argh, it’s one of them, I know!
4. The fourth category… Oh, I know I really should remember this! It’s something I learned when I was a child, I’m pretty sure…

TASK: Use the clues and the 4-way Venn diagram to solve this connect-wall puzzle backwards! Pinpoint the 4 connecting categories, identify the 16 items that made up the intended connecting wall for my puzzle, and tell me which additional item (marked by the white question marks on black in the diagram) links all 4 categories…

Hint: