If you are Sweeny Todd, you're going to need a strop. It's pronounced like drop, but with a an "st" like the sound in strawberry. The color of fresh blood. A strop is a thick piece of leather cord, often used to sharpen a razor. Be hipper than the next hipster and polish up your impressively curling mustache with a freshly sharpened blade. You can even announce that you are stropping the blade, as this noun doubles as a verb. Another use for it is to sharpen the types of blades used in woodworking and give This Old House's Norm Abram a run for his money.
However, if last week you watched the BBC's murder mystery series Grantchester, then you may have heard a maid state that her mistress, "Goes off in strops" because a secondary meaning is to get mad or be in foul moods -- imagine a personality sharpening like a sharp metal object; another way of describing a hissy fit.
The word goes back to Latin stroppus, a thong or twisted cord. The secondary meaning being more modern and deriving from "stroppy"; short for the adjective obstreperous (pronounced: like obstinate + having strep throat + prosperous), or a person who is vocal and impossible to rein in like protesters or noisy school children. Also from the 1600's and also Latin, obstrepere = to clamor against.