Bardcore is arguably traceable to the "What Is Love?" meme which originated in 2005 on YTMND, based on a 1996 Saturday Night Live skit. It consisted of a short, repeated loop taken from the skit of the three "Roxbury Guys" (90s lounge lizards, basically) bobbing their heads to Haddaway's "What Is Love?" in their car. Endless variants and edits of the loop were made -- one of the most memorable being "What Doth Love Be?" which features a medieval-instrumentation version of the Haddaway riff and a Bayeux Tapestry style art work of three men in a boat:
Of course, the song "What Is Love?" on its own makes an excellent bardcore candidate: