It’s part of the legendary phrase used by Johnny Joestar, to kill the 23rd President in Steel Ball Run.
Tusk: CHUMIMIIIN!!! *ripsopen love train* ORAORAORAORAORAORAORA-
Johnny Joestar: hontoni, hontoni, nande dore ma no ichi... Arigato... Gyro.
*valentine fucking dies*
It literally means thanking difusion.
It can be used sarcastically in sentences to thank a person for all the BS a person says.
Basically a normieway of saying thankyou.