mid-14c., enspiren, "to fill (the mind, heart, etc., with grace, etc.);" also "to prompt or induce (someone to do something)," from Old French enspirer (13c.), from Latin inspirare "blow into, breathe upon," figuratively "inspire, excite, inflame," from in- "in" (from PIE root *en "in") + spirare "to breathe" (see spirit (n.)).
The Latin word was used as a loan-translation of Greek pnein in the Bible. General sense of "influence or animate with an idea or purpose" is from late 14c. Also sometimes used in literal sense in Middle English. Related: Inspires; inspiring.