A-slápan

According to the Old English Dictionary:

a-slápan

p. -slép, pl. -slépon; pp. -slápen [a, slápan = slǽpan to sleep] To be sleepy, begin to sleep, fall asleep; dormitare :-- Min sáwl aslép dormitavit anima mea, Ps. Th. 118, 28. a-slapan