Sometimes i think about the idea of Common as a language in fantasy settings.
On the one hand, it’s a nice convenient narrative device that doesn’t necessarily need to be explored, but if you do take a moment to think about where it came from or what it might look like, you find that there’s really only 2 possible origins.
In settings where humans speak common and only Common, while every other race has its own language and also speaks Common, the implication is rather clear: at some point in the setting’s history, humans did the imperialism thing, and while their empire has crumbled, the only reason everyone speaks Human is that way back when, they had to, and since everyone speaks it, the humans rebranded their language as Common and painted themselves as the default race in a not-so-subtle parallel of real-world whiteness.
In settings where Human and Common are separate languages, though (and I haven’t seen nearly as many of these as I’d like), Common would have developed communally between at least three or four races who needed to communicate all together. With only two races trying to communicate, no one would need to learn more than one new language, but if, say, a marketplace became a trading hub for humans, dwarves, orcs, and elves, then either any given trader would need to learn three new languages to be sure that they could talk to every potential customer, OR a pidgin could spring up around that marketplace that eventually spreads as the traders travel the world.
Drop your concept of Common meaning “english, but in middle earth” for a moment and imagine a language where everyone uses human words for produce, farming, and carpentry; dwarven words for gemstones, masonry, and construction; elven words for textiles, magic, and music; and orcish words for smithing weaponry/armor, and livestock. Imagine that it’s all tied together with a mishmash of grammatical structures where some words conjugate and others don’t, some adjectives go before the noun and some go after, and plurals and tenses vary wildly based on what you’re talking about.
Now try to tell me that’s not infinitely more interesting.
Calling out ‘english in middle-earth’ is interesting, and I don’t know if it’s intended as a slight, but the common language in Middle-earth is in fact a pidgin language. (And the humans did, in fact, do the imperialism thing. Sort of. The elves also did the imperialism thing.)
So of the three major peoples of the Edain (Those that would later make up the people of Numenor), they spoke two languages. Taliska and Haladin. Taliska was a creole of several Avari elvish languages with some dwarvish influence(Which is interesting because it’s made a specific note that dwarves like to keep their language in house, as it were, rarely letting outsiders learn it).
Haladin had similar origins but branched off early.
Taliska was further influenced by the most common elvish tongue, Sindarin, and evolved into Adunaic, the common language of Numenor.
Eventually the Numenorians began establishing trading posts and forts (and eventually colonization efforts), which brough them into contact with the local coastal peoples. Since most of the coastal langauges were descended from Taliska, they were able to adopt each others languages pretty easily and from that formed Westron.
So after Numenor fell, Gondor and Arnor rejected Adunaic, and Westron was neglected and mutated further, merging with certain other languages, mostly human. Eventually, the kingdoms started adopting it again and incorporating further elvish additions.
So that then became the common tongue of the western parts of middle-earth, as far est as the Lonely Mountain.
In the books, Tolkien ‘translated’ Westron into English. As an example, Samwise Gamgee’s actual name was Banazîr Galbasi.
(additionally, other languages were ‘translated’. Rohirrim became Old English, and the language of Dale was translated into Old Norse.)