Keyim: means something like "go ahead". Imperative of a verb that is no longer used in the indicative.
Kaam: singular imperative of waam (naam), "goes away"
May be used as a casual goodbye to someone leaving, though it is also a command that can range from a polite, "Go ahead" to a less polite, "Go on, get out of here" depending on tone and context.
Compare to keyima kenaam, suggested in Let's Talk 'Iipay Aa as a farewell to a group of people leaving, translated literally as, "okay, you all can go."
Cuevas suggested this phrase as an alternative to kelu'! to mean, "Go away!"