"th" in Valyrian

[Anthony Appleyard]

The sound "th" is stated to occur in Dothraki but not in High Valyrian, But I have come across "th" in the family surname Baratheon and in the dragon name Vermithor, which characters both occur in circumstances where a Valyrian name might be expected.

 

[The hairy bear]

I wasn't aware of that. Source? I assume it comes from David Peterson's work, and as such, it's not canon and can't be really used to reach any conclusion.

In any case, the two examples that you mention could easily be explained away as not being a Valyrian word. The origin of the name Baratheon (or the identity of Orys' mother) is a complete enigma to us, and it's equally valid to assume that the name is Westerosi in origin (I would favor that hypothesis myself). And perhaps Jaehaerys named his dragon Vermithor as a homage to an epic movie he may have watched in his childhood.

I've found another couple of examples of potential Valyrian th's in Aethan Velaryon and Methyso of Volantis, but an explanation could be found for those too.

[Vaith]

Lorath and Qarth have "th" sounds, too.

David Peterson's Valyrian is a good reference point, but perhaps things were transliterated differently in the Common tongue. Barateon or Vermitor may have sounded unnatural and a "th" sound was added. Additionally Orys Baratheon already spoke Common and so did Jaehaerys I, perhaps they adapted the names a bit.

In the same vein, names like Jon become Ionos in Valyrian according to Peterson. But that did not stop Elaena Targaryen from having a son named Jon Waters.

[Isobel Harper]

Bar means "son" in Aramaic and is used in surnames (both out- and in-world) meaning "son of":

>Baratheon = son of Theon

>Bar Emmon = son of Emmon

The "th" in the instance of Baratheon isn't specifically Valyrian.

On the other hand... one important thing of note is that, historically speaking, there are two distinct cultural branches of Valyrians amongst the Crownlands: Targaryens and an older wave of Valyrian immigrants.  The latter include houses such as Celtigar, Bar Emmon, Velaryon.  (Velaryon, in fact, might just be an alteration of the word Valyrian, a cultural identification that eventually became a family name.)  This branch of Valyrians left Valyria much earlier than the Targaryens and, because of this, there's a subtle dialectal difference between them. 

This difference is exhibited chiefly via their names.  Emmon is a variant of Aemon; Jacaerys is a variant of Jaehaerys.  I also believe the common "ae" in Targaryen names is a variation specific to them and modern High Valyrian AND one that substitutes "au" in other names.  Aurane is a Velaryon; an in-world variant of Aeron perhaps.  Aurion was a Valyrian dragon rider who attempted to conquer Valyria after the Doom; Aerion is a common Targaryen given name.  Following this pattern, we can deduce where Aegon comes from: from Augon, which is a given name in real life.  Other variations of Augon are Auðun and Auðin, ð making a "th" sound.  So, as Aegon derives from Augon, Aethan derives from Auðin/Auðun.

So, there being a lack of a "th" in High Valyrian language but it being present in some names might be a slip up...  OR a sound present in an older form of Valyrian that got lost sometime before the Doom.  (In that respect, Valyrian would parallel German; Old Norse/Old German had ð and þ, but modern German lacks either sound completely.)