Early 17th century; earliest use found in Thomas Coryate (?1577–1617), traveller and writer. Either from resonant, or directly from classical Latin resonantiaresonance.
Definition of resonancy in US English:
resonancy
noun
Resonance.
Origin
Early 17th century; earliest use found in Thomas Coryate (?1577–1617), traveller and writer. Either from resonant, or directly from classical Latin resonantia resonance.