'The lips of a strange woman drip honey...
...and her mouth is smoother than oil. But her end is bitter as wormwood, sharp as a two-edged sword."
This was part of Lincoln Pittridge's sermon towards the end of the movie, which helps explain the movie's title. He was quoting from Scripture, Proverbs 5:3. In various versions of the Bible, "strange woman" is written as "adulteress," "adulterous woman," "forbidden woman," "harlot," etc. I guess "strange woman" is the least lurid of the bunch. Anyway, that's where the title of the movie came from.
"The sword is the soul. Study the soul to know the sword. Evil mind makes an evil sword." — Toranosuke Shimada, “The Sword of Doom“