To have cred, as they say on the street, is to have credibility, almost authority, certainly believability. How does one get some? Consistent behaviour brings credibility as it provides examples that give testimony. Those testimonials, over time, build personal character credit, just like a history of financial stewardship can build a financial credit line. If I have cred people will back me up, support me.
A credential is a recognition of having attained/learned an ability, usually confirmed with testing of some kind. Credentials bring the image of papers with signatures and maybe official stamps etc. Those papers are issued by the testing agent. Getting a credential can take a long time. Getting your papers, some call it, is often a rite of passage into a profession. The credential is proof that you belong there.
To be credible is to be many positive things. To be incredible… wait, isn’t that supposed to be good too? If I say incapable that means not capable, but incredible means over the top, amazing, unbelievable and may not refer to credibility at all. Is the English language incredibly strange or what? I could be incredibly irresponsible. That does not sound good like Mr Incredible and the whole Incredible family.
I can gain credits by shopping at certain stores. Those, if I collect enough of them, give me credit toward future purchases in that store. Can I gain credit, become more credible from/with another person? If you feel that I am credible you might lend me your bicycle. If not, you probably wouldn’t. Politicians have a big challenge with credibility. Their credibility seems to go up and down. Inconsistency equals low credibility.
To be discredited is to undo credibility, to be stricken from the rolls of the membership and to be denied privileges. It takes a long time to become creditable and even longer to regain credibility if lost. Being credible is to be trustworthy. If I have at some time been discredited, even if the accusation is not true, it can be very hard to receive the trust of others again. Well, I think you are credible. Just saying.