At what point did condoms evolve from a post-coital treatment for syphilis, to something worn during intercourse to prevent venereal diseases and/or pregnancy?

I've seen multiple sources cite Gabriele Falloppio as authoring the earliest uncontested description of condom use. According to this article, Falloppio described a linen sheath soaked in medication, to be used after intercourse to cure syphilis.
At what point did people realize that preventing venereal diseases (or pregnancy) required a barrier during intercourse?