1560s, "engage (the attention of) beforehand, engross in advance of or to the exclusion of other things," from pre- "before" + occupy. Sense of "occupy before others" is attested from 1620s. Related: Preoccupied; preoccupying.
the army preoccupied the hills
prenup
prenuptial
preoccupancy
preoccupation
preoccupied
preoccupy
pre-op
pre-ordain
pre-order
pre-owned
prep