Definition of "unfrank"

That unknown, approaching thing, seemeth ever ill, my brother, which must have unfrank heralds to go before.

1852, Herman Melville, Pierre; or, The Ambiguities

Hitherto I have lived a great deal too much apart from my sisters, partly from indolence, and partly from my unfrank disposition.

1926, Beatrice Webb, My Apprenticeship, published 1979, page 72