Thal is "Tal" since 1903 ("dale" is the related English word). In 1903, we dropped all h's after t's except (1) in words of Greek origin like "Theater" and (2) in "Thron" ("throne") due to an objection by the Kaiser and (3) in "Thing" (assembly of all men) which was forgotten to be changed I have heard. We never pronounce a th any different than a simple t. Of course, the old spelling remains sometimes in place names and family names.

The Neanderthaler was found before 1903, when that valley was still the Neanderthal. It now is of course the Neandertal and we call that species Neandertaler.

"Thyme" (Thymian we say) I considered for at least two decades to be pronounced as tyme only be Irish like Christy Moore whose version of Bunch of Thyme was the only I knew then. Only when I heard it sung as "tyme" by an Englishman I had a look into the dictionary.

How came it that Thyme (of Greek origin) is pronounced so differently from the many other words of Greek origin (Theater, Anthropology, rhythm, theism) or do I have to learn a new pronunciation for those words as well?

Wolfgang