(Under) implies that the weather is rough and the wind so high that the ship displays no sails on the masts. Figuratively applied to a man reduced to the last extremity. Figuratively, a disingenuous person sails under bare poles.
“We were scudding before a heavy gale, under bare poles.” —Cupt. Marryat.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894