incubate v.

1610s, "a brooding," from Latin incubationem (nominative incubatio) "a laying upon eggs," noun of action from past participle stem of incubare "to hatch," literally "to lie on, rest on," from in- "on" (from PIE root *en "in") + cubare "to lie" (see cubicle). The literal sense of "sitting on eggs to hatch them" in English is first recorded 1640s.

"apparatus for hatching eggs by artificial heat," 1845, agent noun from incubate (v.). Late Latin incubator meant "one who lies in a place."

"imaginary being or demon, credited with causing nightmares, and, in male form, consorting with women in their sleep," c. 1200, from Late Latin incubus (Augustine), from Latin incubo "nightmare, one who lies down on (the sleeper)," from incubare "to lie upon" (see incubate). Plural is incubi. Compare succubus.