Yours, Etc.: Origins and Uses of 8 Sign-Offs
"touching the feelings intensely," 1630s, figurative present participle adjective from penetrate (v.).
1520s, from Latin penetratus, past participle of penetrare "to put or get into, enter into," related to penitus "within, inmost," penus "innermost part of a temple, store of food," penates "household gods." Related: Penetrated; penetrating.