Be redtom

• be damned!

• by Dermot! → be dermot in line 14 above

• Dermot: Diarmuid; in the Finnian tradition of Irish mythology, Diarmuid and Gráinne are the counterparts of Tristan and Isolde; Diarmuid was the nephew of the Irish hero Finn Mac Cool; Gráinne, the daughter of the High King, had been promised to Finn, but when she saw that he was too old she cast a love spell on Diarmuid and the two eloped; they ran away but Finn's pursuit prevented them from spending two consecutive nights in the same place; megalithic monuments in Ireland are still referred to as "the bed of Grainne and Diarmuid"

• by bedtime

• by red time: (i.e., by sunset, or if the rain signifies stormy weather, it is morning according to "red in the morning, sailors take warning")

• be red tom: Grace O'Malley is often pictured with red hair + tom could be a reference to her taking on masculine qualities, as in 'tomboy'