Definition from Wiktionary, the free dictionary
From Middle English forslepen, equivalent to for- + sleep. Cognate with West Frisian forsliepe (“to forsleep”), Dutch verslapen (“to sleep off, sleep away”), German verschlafen (“to sleep away, oversleep”).
- (intransitive) To be overcome with sleep.
- (transitive) To neglect through sleep or by sleeping; sleep through; oversleep; sleep off.
1890, Matteo Bandello, The novels of Matteo Bandello: bishop of Agen:
- At this moment, Giulietta, who had already forslept and digested the virtue of the potion, awoke and feeling herself kissed, misdoubted her that the friar, being come to take her up and carry her to his chamber, [...]