bʰeydʰ-
“to trust, to confide”trust, confide, persuade
Root for trusting, yielding Latin fidere (to trust), Greek peithein, English abide.
Discussion
The root *bʰeydʰ- expressed trusting, confiding, and placing faith. Latin fīdēs ("faith, trust") produced fidelity and infidelity, confide and confidence ("trusting together"), fiduciary (holding in trust), and federal and federation from foedus ("treaty, compact"). The word fiancé traces from Old French fiancer, "to pledge." Latin fīdus ("faithful") gave perfidy ("through-faith," ironically meaning its destruction) and the name Fido, the archetypal loyal dog. In Germanic, English bide and abide preserve an older sense of trusting in endurance — to abide is to remain steadfast, to wait with confidence. The semantic development from "to trust" to "to wait, to endure" reflects a profound insight: true faith is inseparable from patience. Pokorny (117) established the reconstruction. The root underpins the entire architecture of trust in Western civilization, from religious faith to legal compacts to the quiet personal resolve of simply waiting.
Notes
Pokorny 117. English faith, confide, federal, abide, bide.