It’s actually possible to do a reverse search with TLG dictionaries (LSJ, Powell, Cunliffe).
http://stephanus.tlg.uci.edu/lsj/#eid=1&context=lsj
Before typing word you’re looking for, select “meanings”, and click “go”. For “thumb”, we apparently have τὸ ἄκρον τῆς χειρός, ὁ ἀντίχειρ (sc. δάκτυλος) and ὁ ἀντίχειρος δάκτυλος. They don’t look like common words, but they’re very logical – the last two ones actually relate to the function of the thumb, i.e. opposition to the other fingers. Also, with this search, I got to explore the original sense of θέναρ and ὑποθέναρ…
Thumbs are actually a pretty important part of a functional hand. I’d give up the other eight fingers and eight toes (but not the big toes) to save one thumb. Likewise, big toes are surprisingly important for walking (not to mention running). On the other hand, I’d give up a large number of smaller toes to be able to read Greek better.
About Herodotus’ use of sources: he didn’t have many reliable ones. There were close to no written sources, although probably he got something from his Greek predecessors. Apparently he didn’t know other languages, and written Eastern sources were worthless propaganda anyway. A good modern historian could probably have done a bit better, but not much –for example, instead of saying “the Egyptians say” and “the Persians say”, he or she would have been more specific. But he or she couldn’t have helped the fundamental fact that Herodotus’ sources were what they were, distorted oral accounts. It’s often said that after 70 years have passed, events are gone out of living memory. I think this explains many things in the modern world as well: take the anti-vaccine movement, for instance: what’s happening, I think, is that fewer and fewer people alive in the Western world today remember dangerous infections like the polio and what they can do.
Thucydides is aware of this problem, and for that reason he writes contemporary history. Even Herodotus is aware of it to some point - in the beginning of his book, he ends the story of the abductions of women by saying something to the effect that “I really can’t tell if it all happened like I said or in some other way - so instead, let me tell you about Croesus”. I think the story of the abducted women acts as foil, in a way, to what follows. Herodotus doesn’t want to write mythology, he wants to write real “history”. He knows that in mythology, the question whether something really happened or not is irrelevant, and he doesn’t want to do that; he wants to write about events where the question is relevant, even if it’s not answerable. But it is true that he likes a good story more than anything, and sometimes we wonder if he could have tried just a little bit harder to see what’s behind that good story.