The only free and comprehensive online etymological dictionary of the Spanish language
hermoso (Adjective) "beautiful"
Early 12th cent. Old Spanish fuermoso. From Latin formosus 'id.,' from forma "form," "beauty" and -osus (see forma and -oso respectively).
Also the origin of several surnames, including Hermoso, Hermosa, Hermosel, Hermosilla, Hermosín, Hermozin, and Ricohermoso.
Asturian formosu, Portuguese formoso, Galician fermoso, Catalan formós, Italian formoso, Romanian frumos

Appendix Probi (3rd or 4th cent.) records formunsus.