fides is translated into English by all the key words above – but most often today by faith
unfortunately the term faith has been hijacked by bigbuck religions to mean a belief system. This is clearly how the word is used today – a man of faith, the inter-faith council, etc. – yet these are belief systems in which a rational man cannot place confidence (the other strongest translation) since, by definition, belief is based solely on itself rather than on evidence.
I would rather place my faith in the powerful possibility that the sun will rise in the east tomorrow [or more accurately, will appear to rise in the East] precisely because that is where it has risen every day of my life previously. I do not have faith that anyone has risen from the dead, because, religious fables notwithstanding, there is no evidence anyone ever has. The bible is not an historical text. It was a cut and paste job of many hands over many centuries, with the same basic political agenda. Serious study of scripture has led more than one aspiring preacher to become an atheist! Know the truth and the truth will set you free. (John 8:32)
and lastly, the linguistic link between stringed instruments and credibility…just might result in the expression “gut feeling”…as the strings were traditionally made of catgut.