The story
From jarty and cuck. Jarty is a clipping of the name jakparty.soy, a now-defunct spinoff website of soyjak.party, which was heavily associated with rampant paedophilia and other reprehensible behaviour. The jak part derives from Wojak, a series of caricatures used as expressions by online users.
Etymology from Wiktionary, CC BY-SA 4.0.