The source was "Gothic Armor" from Diablo -- I never thought that sounded silly, but I'm not a native speaker. Anyway, this is one name that I'm least sure of, so do you have a better suggestion? There's a armor "Gothic Armor" too. They are absurdly heavy, and reduce speed and knockback, but have really high protection. I thought of "Moloch Armor/Boots" as a name instead, but that would be silly too? (and a reference to adom ^^).
Anyway, they were called "Gothic Hell Armor/Boots" before that, so note the improvement ^^.
P.S. There's another set called "Phaseshift Armor/Boots" -- does that sound silly too? And a cookie for anyone that will know* what they reference too :D.
* Googling doesn't count
Tastes vary, of course, but I would suggest something such as 'Unholy Boots' or 'Unholy Armour'. If you're giving a boots and armour the same name though, that suggests (to me, at least) that they're a set, and that they either have very similar effects, or that you gain bonuses for equipping them both at the same time. If neither of these is the case, I'd suggest changing their prefixes slightly.
Anyway, some possible names, off the top of my head:
Unholy Boots/Armour
Sin's Durance Armour (Durance means imprisonment... Which conveys the idea that they would limit your movement speed, yet offer high protection).
Moloch's Armour/Boots (A good idea, but I'd add the apostrophe s - Moloch is a famous demon/god).
Boots of Belial
Armour of Asmodeus
Full-Body Armour
Regarding GenTechJ's point, Gothic Armour doesn't sound silly, as it is a legitimate type of armour - made in the German region (yes, in the middle ages) - but Gothic Boots, to me, do.
'Necroarmour' also sounds a bit cheesy. 'Necromantic Armour' would be better, IMHO.