Early 18th century; earliest use found in Jeremy Collier (1650–1726), anti-theatrical polemicist and bishop of the nonjuring Church of England. From un- + menacing.
Definition of unmenacing in US English:
unmenacing
adjective(ˌ)ʌnˈmɛnɪsɪŋ
Not menacing; unthreatening.
Origin
Early 18th century; earliest use found in Jeremy Collier (1650–1726), anti-theatrical polemicist and bishop of the nonjuring Church of England. From un- + menacing.