Dubious derives from the Latin verb dubare, meaning "to hesitate in choice of opinions or courses," and it is related to the Latin word for "two": duo.

Where did the word all originate?

all (adj./adv.)

Old English eall "every, entire, the whole quantity of" (adj.), "fully, wholly, entirely" (adv.), from Proto-Germanic *alnaz (source also of Old Frisian, Old High German al; German all, alle; Old Norse allr; Gothic alls), with no certain connection outside Germanic.

What does ethically dubious mean?

If you describe something as dubious, you mean that you do not consider it to be completely honest, safe, or reliable. [...]