You know, I've seen Van Helsing twice but can attest to being preoccupied w/something else while watching it so although I do recall the LHoG one, don't recall him being called Gabriel, but it makes sense.
It's actually a rather "quiet" portion. Van Helsing and Dracula are "stalking" each other, and Dracula almost whispers "Gabriel. Oh Gabriel.", if I remember right, just before Van Helsing stakes him (attention grabber). In the same conversation, he says something about "It must be so hard to be the left hand of God.", but that's all it really touches on.
That was one of my main frustrations with that movie. Why didn't they explain that? And the whole nightmares thing? Wasn't explaining that one of the main reasons they went there?
It's implying that Van Helsing is the human incarnation of Gabriel, and when he mentions to the friar about "I remember Rome", it's implying that Van Helsing has been around since roughly the time of the crucifixion. At another point, Dracula mentions that he can tell Van Helsing much about his past, and that's supposed to be part of the "bait" for Van Helsing to not kill him, and probably why it doesn't expand from that.
On a related note, if you haven't seen "Shroud" (made in 2009), the ending is interesting, and related in some way (which I won't spoil).
As for blasphemous for calling a sword Gibril or Gabriel - I don't see why a different language of the same name would matter, so Gabriel, Gibril, same thing. Calling a sword what it's been named is, simply, a name. As long as you don't worship the sword, I'd say you're fine, I think.
