fiducial \fi-DOO-shuhl, adjective:

1. Based on or having trust: fiducial dependence upon God.
2. Accepted as a fixed basis of reference or comparison: a fiducial point; a fiducial temperature.

Knowing the sincerity of her concern for my well-being as I did, I can say with fiducial confidence she was attached to the phone, where she’d no doubt made a beeline the very moment after I’d stormed out of the house, awaiting a call from me announcing I was alright.
— William Cook, Love in the Time of Flowers

No, it was a par excellence speech, one that neither he nor anyone else was to give in front of an audience, one that wasn’t going to be subjected to criticism, for how can you compare when you have no fiducial point?
— Thomas Justin Kaze, The Year of the Green Snake

Fiducial comes from the Late Latin word fīdūciālis meaning “trust.”