strop · noun, verb1
Same as strap (which see); recorded in English since 1702. The verb sense referring to honing a sharp edge is recorded since 1842.
strop · noun2
Back-formation from stroppy.
strop · verb3
From apostrophe, due to use of apostrophes as single quotation marks to indicate boldface in ALGOL 60. Other methods were used, especially in ALGOL 68, where the earlier matched apostrophes were no longer common, and the term became used more generally for any such method.
Etymology from Wiktionary, CC BY-SA 4.0.