This Christianese word is kind of the opposite in meaning of the English word that's spelled the same.

In English, to witness is to see or observe something. In Christianese, to witness is to tell people what you believe, in an effort to convince them to believe the same things and/or to join your religion. (AKA to "get saved".

)
I said these words are
kind of opposite. Christian witnessing isn't talking about what you have
seen (usually). You haven't
seen Jesus after He rose from the dead, for example. You
believe He has risen, because you believe written reports. Unlike the disciples (
not just Thomas), you are expected to believe without seeing. Or, at least, you will be blessed if you do. (So it says.)
None of
them believed, until they actually witnessed (English!) Him living again. Even the women didn't believe until they saw Him. (That's what it says. You could look it up.

)
Anyway, yeah, it's kind of funny how you guys use some words that
look like they're English words, but aren't.