Answer:
The vast majority of Spanish words ending in -umbre are derived from Latin umbra, meaning "shadow." This word was used to describe various things associated with shadows, including darkness and gloom. Over time, the meanings of many Umbre-derived words have shifted somewhat away from their original connotations, but they still often retain a sense of mystery or foreboding.
Some examples include:
*sombra (shadow)
*penumbra (partial shadow)
*lumbrícas (earthworms)