actually many words used to be written with "th" too in German, but are no longer (e.g. Thron/Tron, Thon/Ton).
To spell "Thron" with th (and some other waords as well) was fashonable during the 18th and 19th centuries.
Sorry, guys, but did I miss something?
Thron is
still spelled with th.
There was neither an etymological nor a phonetic reason for this.
Who says so? At least, it depends. Sometimes it was Greek words having a
θ (theta) in Ancient Greek that were spelled with
th in German. So the etymological reason is clear:
Theater (
θέᾱτρον)
Thrombose (
θρομβώσις)
Theorie (
θεωρία)
Thron (
θρόνος)
Thunfisch (
θύννος)
Thymian (
θύμον)
Theke (
θήκη)
These (
θέσις)
Thermo... (
θερμός)
Theologie (
θεός + λόγος)
Thema (
θέμα)
...
However, you're right that most German words used to be spelled with "th" without any further reason: Thor (das/der), Thür, Thran, ...
Other words, like Tiger, Tisch, Teufel etc. were always like they are spelled today.
It just made the word look more important.
I don't believe that that was the reason. Why should a Tür be more important than a Tisch?
Middle High German spelling was definitly whithout an h.
That is not necessarily true. The Middle High German spelling of "Thron" was both trôn and thrôn, tymian and thimean, ...
The rule about the "th" in German is not consistent at all; you just have to memorize which words are spelled with or without "th".
And to come back to the original question: No, there's no difference in pronunciation between "Trom..." and "Throm...".