incuba

incuba , evil spirit, demon which has sexual intercourse with woman while she sleeps. ~a, mære GlC I 225; s1150 de cachodemonis ~e (v. cacodaemon); quidam puer a quodam demone ~a, ut dicitur, generatus M. Par. Min. III 61 (cf. id. Maj. V 82); duo fuerunt igitur Merlini, ut asseritur: / unus dictus Ambrosius ex incuba progenitus, / ‥ Eul. Hist. II 137.