Sorry, but the pagan holiday Samhain was around long before the Christians came to be. Do you believe everything you read on Google?
We're not talking about Samhain, are we? We're talking about Halloween. Samhain is a pagan holiday. Halloween is a Christian holiday.
Yes, Samhain predates Christianity, but like many pagan holidays, it was usurped by the Church for its own uses.
Samhain is gone...replaced by Halloween. Halloween, even in its name, is a Christian holiday, not a pagan one.
We could look at Easter, Christmas, and some other holidays as well, and find their pagan equivalent on the calendar, too, if you'd like.
The holiday bearing the name Halloween is a Christian invention, set up to replace the old Celtic pagan holiday. The Church in that time found it convenient to supplant those pagan holidays with ones more appropriate for Christians.
Even the name Easter has pagan roots....it was coopted by the Church, but held its name. A nice fertility festival for the pagans got converted to a resurrection festival. Oddly enought, it had pretty much the same function for the pagans...just a different religious emphasis. The dead plants coming back to life again after the cold winter, or the Messiah coming back again after the crucifixion. Very nice that the two ended up being celebrated at the same time, eh? Worked out well for the Church, too.