Tallwen is, without doubt a fictional name.
Still, in fantasy books names invariably imitate some lamguage (e.g. in place names in Sapkovsky books, quite popular in Russia, I easily recgnize Celtic influences). Definitely I associate "Wenwei", "Dariana' and "Jack" with certain ethnicities, and "aegis" with a number of things, from Greek mythology to the modern missile defence.
So Dariana's question about 'subtext' cerainly makes sense.
Now we are dealing with fictional fantasy TV-series discussed in a non-fantasy book! These names are likely to be parodizing something... and are more likely to actually mean something.
Unfortunately, i only recognize 'fokken' in 'Stelterfokken'... which is a Dutch cognate for English F-word. Less obsene, though. It totally makes sense in a parody.
Stelter says nothing to me.
Tallwen seems to be tall+wen, where tall- must be just 'tall',
while -wen... In happens in Welsh female names. From masc. gwyn / fem. gwen "white". Gwendolin and Jennifer have the same element. Irish 'Finn' is a related word.
I believe, such an ending may happen in fantasy books in female names... but i can't recall many Another possibility is corruption of 'win' in old Enlglish names like Edwin.
I don't know what the author (or a typical Engish reader) associates siuch a name ending with. I, personally, assotiate it with female names.
The answer is in the sentence.
The Stelterfokken is a tribe. A tribe is a group of people. Tallwen is a member of the tribe.
So, Tallwen is the name of a person.