Why do we shorten Gadreel’s name to Gad? I mean, sure, it’s the first syllable (and I think it’s also a real name in the Old Testament?), but do you really say Gad-reel? NO, you practically pronounce it as G'dreel. There is ZERO emphasis on the Gad, not even like with Castiel/Cas where the first syllable may not be the primary stress, but at least it still sounds like Cas. But with Gadreel, the vowel sound in Gad just virtually isn’t there.
I prefer to nickname Gadreel, Dree. It makes way more sense, phonetically. And also it’s really, really cute.