The etymology is interesting - Pebble Voting was used in the early democracies in Greece from 500 BC. Black pebbles meant 'no' and white meant 'yes'. The tradition evolved to the black and white marbles used in the Roman senate centuries later, i.e. two millennia ago. The practice has since continued – it was used in the early American republic in the 18th century, and the word 'ballot' used today for voting means just that - a 'little ball'.

The word 'blacklist' probably originated from this meaning. It was in use in England since before, but it was probably the "Black List of Regicides” that popularised the term. It was a list compiled by the administration of King Charles II England of those to be punished for the beheading of his father King Charles I in 1649, following the restoration of the monarchy of England in 1660. As this list was rather long, it was a probably a bit of a traumatic event for the gentry in London and it’s not hard to imagine that the memory of the dreaded "blacklist" stuck. A century later the word was in general use for a list of enemies, detractors, and unwanted people.

Conversely, "in the black" is the notion of having no debts or a positive cash flow. This obviously comes from the centuries old principle of using black for credit, and red ink for debit and negative balances in the double-entry accounting system codified in the 15th century.

A tangential but equally fascinating concept is the practice of forbidding - or blacklisting - words in totalitarian regimes like Maoist China. Controlling language was a key strategy to influence thought, define in-groups, and ostracize out-groups. It's a hallmark of a totalitarian systems aiming to shape thought through language. Very much not at all in line with the principles of ballot voting in a democratic system one should think.

(The last argument can be used with any word. I could find your Gallicism offensive and demand that all words with a French etymology should be removed from English to restore it to it's Old-English form before the oppressive Normand rule, since after all, the old words would just make more sense to those who are old enough to be used to it, and my feelings are important.)

To me (where English is a second language), Allowlist and denylist seem unclearer. Is it a block list, a exclude list, or a permission list? Allow/deny would lead me to the last one, as in authenticate users who has some permissions but not others.

Blacklist and whitelist would be closer to include/exclude, so the replacement would be a includelist and excludelist, or include/exclude as shorthand.

Allowlist/Denylist are clear and perhaps more specific, but blacklist/whitelist are not arbitrary, they're just using black in valid ways according to common English dictionaries, which is similar to how other languages use the word black, but it is less specific.

> If you'd like to explain Why the word means what it does I'd love to hear it

Simply because black means different things depending on the context. Evil, invisible, mysterious, absence of light, sinister. It's not arbitrary because that's how the word black is commonly used.