fi·du·cial (fĭ-dshəl, -dy-, fī-)
1. Based on or relating to faith or trust.
2. Relating to or characteristic of a legal trust; fiduciary.
3. Regarded or employed as a standard of reference, as in surveying.
[Late Latin fīdūciālis, from Latin fīdūcia, trust, from fīdere, to trust; see bheidh- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.