What does the “‑to” ending mean in most English words that end in “‑to”?

Solution 1:

I’m not sure what you mean by asking what the meaning of words that end in -to is, because -to is not really an English suffix in the general case. As you note, it occurs in many words with no overlap in sense, like alto, auto, biscotto, burrito, canto, cornetto, ghetto, grotto, potato, lotto, magneto, mosquito, panto, photo, presto, recto, veto. Many of those derive from Latin or its children, but their -to has no meaning of its own.

Nonetheless, for your case of the adverb hitherto, there actually is something here behind it. Just as with adverbs like today, tonight, and tomorrow, the to part was originally part of a longer adverbial phrase involving a preposition that was originally worn down into a single word in examples like hereto, hereunto, hitherto, hitherunto, thereinto, thereonto, thereto, thereunto, thitherto, whereinto, whereto, whereunto, and whitherto.

In all those, to represents what was once the preposition to.

Solution 2:

A good test is to see whether you can break off the "to" and still have a valid word. In the case of "tomato" and similar words, you can't: "toma" isn't a word, so the "to" you broke off isn't either.

But "hither" is a word ("in this direction"), so the "to" is also. In combination they don't necessarily have a meaning that can be predicted from the meanings of their parts, but there's usually at least a distant relationship.

Solution 3:

The answer is, it means "to".

Note that you can use "to" with times.

So, "I'm at work 9 to 5".

It's that simple.

"Hither" basically means "towards", "up to", "that side of".

"Hither to" just means "up to that time".

The "to" part simply means "to", as in "up to" or "through to" or "9 to 5".

As others have explained, there is no general case; it's not "a suffix".