Yellow archangel (Lamiastrum galeobdolon), if anyone was curious.
It means that it's Linux shaped as an arch.
Those are different, prefix "arch-" comes from greek "ἀρχι-", while noun "arch" is from latin "arcus".
Though, it should be mentioned that initially the meaning was taken from the prefix one, it's just with time everybody got used to the Arch arch logo and spelling, I suppose.