Many of them seem written like crossword clues, but I've run searches on them with no consistent results. I'm assuming that we're looking for a word sequence using definitions he's made up, which I explored a bit last night.
Here's what I cam up with (parentheses are ones I'm pretty unsure of):
In that case "This" is obviously a "Puzzle". The only thing that comes to mind for "Anciently written with TH" is the third person singular conjugations of English, e.g. "knoweth". So... "S"?
"We didn't leave the Stone Age, because we ran out of stones."