E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Off (Saxon, of; Latin, ab, from, away).
The house is a mile offi.e. is away or from us a mile. The word preceding off defines its scope. To be well off is to be away or on the way towards well-being; to be badly off is to be away or on the way to the bad. In many cases off is part of a compound verb, as to cut-off (away), to peel-off, to march-off, to tear-off, to take-off, to get-off, etc. The off-side of horses when in pairs is that to the right hand of the coachman, the horses on his left-hand side are called the near horses. This, which seems rather anomalous, arises from the fact that all teamsters walk beside their teams on the left side, so that the horses on the left side are near him, and those on the right side are farther off.
He is well off; he is badly off. He is in good circumstances; he is straitened in circumstances, étre bien [or mal] dans ses affaires. In these phrases off means fares, he fares well [or ill]; his affairs go-off well [or ill]. (Anglo-Saxon, of-faran.)