opener (n.)

Old English openian "to open, open up, cause to open, disclose, reveal," also intransitive, "become manifest, be open to or exposed to," from Proto-Germanic *opanojan (source also of Old Saxon opanon, Old Norse opna "to open," Middle Dutch, Dutch openen, Old High German offanon, German öffnen), from the source of open (adj.), but etymology suggests the adjective is older. Transitive sense of "set in action, begin, commence" is from 1690s. Open up (intrans.) in the figurative sense "cease to be secretive" is from 1921. Related: Opened; opening.

"instrument for opening one end of a sealed tin can," 1868, from can (n.) + opener.

1864 as a device to slit open letter envelopes, from letter (n.1) + opener. Earlier as a government or other official on continental Europe in charge of opening and reading private mails of suspected persons and censoring them (1847).