"time intervening," 1560s, from Latin interim (adv.) "in the meantime, meanwhile," originally "in the midst of that," from inter "between" (from PIE *enter "between, among," comparative of root *en "in") + im, ancient adverb from stem of pronoun is "this, that." As an adjective from c. 1600.
an interim agreement
interflow
interfold
intergalactic
intergenerational
interglacial
interim
interior
interiority
interjacent
interject
interjection