1570s, "emit semen," from Latin eiaculatus, past participle of eiaculari "to throw out, shoot out," from ex- "out" (see ex-) + iaculari "to throw, hurl, cast, dart," from iaculum "javelin, dart," from iacere "to throw" (see jet, v.). Sense of "exclaim suddenly" is from 1660s. Related: Ejaculated; ejaculating; ejaculatory.