Do the Hobbits speak only Common? Throughout the movies we hear a lot of Elvish, some Black Speech, some Dwarvish, lots of Orcish, some Treeish(?), but the Hobbits only ever seem to speak Common.
How in the hell do the Uruk-hai come hatching out of pods in the ground knowing not only Orcish and Common but also knowing idioms? I guess maybe Saruman used some magic to give them a Rosetta Stone session or something?
The Hobbits only speak Common, yes. Specifically, although it’s not very clear in the films, a slightly changed and simplified version of it, where for example (as in English) there is much less distinction between familiar and formal language - which is one of the reasons that Merry and Pippin were taken to be Hobbit nobility, their speaking in familiar terms to Théoden and Denethor.
The pods seem to be solely an invention of the films, presumably because the compressed timescale doesn’t allow for the breeding and teaching of Orcs. I’m not sure there’s an Orcish language distinct from the Black Speech, though.
“Treeish” would be Entish, and there’s also the language of Rohan as distinct from Common, although I’m not sure it’s heard much in the films.
I believe “Common” is known in the books, also as “the Westron tongue”: a language with various dialects / sub-groups, originally that of humans (including for this purpose, hobbits) pretty much throughout the west of Middle-Earth; which has fallen into use over the centuries, as a handy global “Esperanto” in which all races / types of being can communicate with each other. I seem to recall from the books – may have this wrong – that the Rohirrim’s language is in fact a dialect of “Common / Westron”; the speech of the hobbits being – as Steophan indicates – another dialect of same.
I think the books mention now and again – as well as the Black Speech – “Orkish” languages; references in passing, to Orcs speaking with each other in “Common” (thus, understandable by their captives) because different tribes of them speak different “orc-type” tongues. The Black Speech is, I believe, a device of Sauron (and other “big bads”?) to “refine” orc-speech into an orderly and grammatical and impressive – though deliberately, hideously ugly – language: which they would wish, after they are victorious, to have supplant the Common Tongue as Middle-Earth-wide means of communication.
The hobbits speak a dialect of Common (AKA Westron, AKA Adunaic), but Rohirrim is a different language, related and partly ancestral to Adunaic (hence, just as Tolkien rendered Adunaic as English, he rendered Rohirrim as Anglo-Saxon). Adunaic also has some heavy Elvish influences.
There are actually two main Elvish languages, Quenta and Sindarin. Among the elves we see in Lord of the Rings, Sindarin is more common.
Orcish is a dialect of the Black Speech. Or rather, a whole set of dialects, some of them fairly widely divergent: The orcish languages of different regions (like Mordor and the Misty Mountains) are so different that when orcs from those regions are forced to work together, it’s easier for them to converse in Adunaic than to try to understand each others’ dialects.
And part of the reason that Merry and Pippen were taken to be nobility is that they are, or at least, the closest thing the Shire has to nobility. Pippen is a Took and the heir to the Thane, the official representative of the King in the Shire, and Merry is a Brandybuck and the heir to the Master of the Hall, the ancestral masters of Buckland (the portion of the Shire across the Brandywine River).
I always found it amusingly ironic that after chasing Sharkey’s men out of Shire, Sam, Merry & Pippin quietly but inevitably became the Mayor, the Master & the Thain, are granted extraordinary powers by Aragorn, and for decades hold the Shire in their iron fists.
I can’t, just now, find my copy of LOTR with the appendices; but I’m sure I recall a language-related appendix statement, to the effect that – as Steophan writes – part of the reason why M & P were reckoned to be nobles in their country, was their addressing human rulers, in “familiar” language – although that was just, the way they knew how to talk ! Also, as you say,it was partly that they were indeed from the Shire’s ruling classes; though I suspect that the whole idea of a hobbit “nobility” struck the high-ups of the human kingdoms, especially Gondor, as comical.
It’s specifically that in modern English we no longer have the thou/you distinction, like French has tu/vous. Whilst Merry and Pippin may have been the closest thing to nobility in the Shire, their position wasn’t really comparable to that of a Prince, as Pippin was taken to be in Gondor. (Ernil i Pheriannath in Elvish).
To quote from Appendix F, part II to The Lord Of The Rings
This explains some of the relationship between Pippin and Denethor, another thing not particularly well represented in the films.
The funny thing is that English actually lost its familiar pronouns, and only kept the formal “You”. We tend to think that “thou art” is some stuffy form of address, but it was actually the informal, and “you are” is the formal.
To be fair, the extended versions of the films, although entertaining to me, are already very long; if everything was explained in detail in the films, we’d have like 14 4-hour films. Some stuff just has to be cut out for a film version. That being said, I thought it was well enough represented that Pippen offered his service to Denethor with politeness and courtesy, even though he had presumably never been in the presence of any human Lord of any kind; Pippen had previously mostly been shown as a bumbling fool of sorts, this time he came off as maybe not of regal bearing but at least something more than Jar Jar Binks.
He had (albeit briefly) previously met King Theoden, at Isengard, as well as traveling with Boromir for an extended period of time. Neither of them were quite at Denethor’s rank or bearing, of course.
He’d also traveled with the heir presumptive to the throne of Gondor for months, though Aragorn carried himself far differently, of course. 
Well, Sam was democratically elected Mayor eight times, although by the end the hobbits were sick and tired of the “Make the Shire Great Again” hats and were glad to see him head out to sea…
True. Maybe he picked up on some cultural cues of some sort along the way.
To expand on this, the original modern English second-person pronouns were “thou/thee/thy” in the singular case and “ye/you/your” in the plural case. But the singular case began to be used only in familiar settings. So the plural case began to be used as singular when in formal settings. Eventually, the familiarity restrictions eliminated usage and plural case came to be used in all settings, and the singular has become archaic.
Because English still likes to keep a distinction between the singular/plural cases, there is a draw towards a new form for the second-person plural case. Hence innovations like “you-all”, “y’all”, “you-ones”, “younz”, “yinz”, “youse”, “you-guys”, etc.
Also note, that complaints that using “they” for third-person singular would be confusing are ignoring that modern English has already made the plural-to-singular transition in pronouns once before. While confirming that the singular-plural distinction is important. Maybe we need to introduce “th’all”.
I didn’t know that. So they’re basically Amish?
I don’t know whether Gondor had the concept, but if it did, Aragorn would be the heir apparent, not heir presumptive. There was no one around who could displace Aragorn in the line of succession by giving birth to a son.
I wondered if I’d used the wrong term. I now see that I did. Thanks for the clarification – I’ve learned someting today!
I’m not sure it’s correct to call Aragorn any sort of heir. The throne was his; he already inherited it from his father. He just hadn’t claimed it yet.
True, he had already inherited the throne, so neither heir presumptive nor heir apparent. He was the king. But he was still an heir of some kind in the sense that he was his father’s heir.
In a strict legal sense, a living person doesn’t have heirs, so that’s why a living monarch would might have an heir apparent or an heir presumptive, but won’t have an heir (period) until he or she dies.
I find the singular “they” consistently confusing. And I tend to use “y’all” for plural you, even though I’m a yankee, because that’s often confusing, too.
Maybe I should just start proactively saying “they all”.
Though, at that point, he hadn’t claimed the throne / been crowned / etc. I’m not sure if there’s a term for that.