The Spanish word 'horroroso' (meaning 'horrible' or 'frightful') comes from combining the Spanish noun 'horror' with the suffix '-oso' (meaning 'full of' or 'characterized by'). The Spanish 'horror' traces back to the Latin word 'horror' meaning 'dread' or 'terror', which itself derives from the Latin verb 'horrere' meaning 'to bristle' or 'shudder' - likely referring to the physical sensation of one's hair standing on end when frightened.

The addition of the suffix '-oso' to 'horror' creates an adjective that literally means 'full of horror' or 'characterized by horror', similar to how English forms adjectives with '-ous'.

The simpler and more common Spanish word 'horror' is directly related to 'horroroso'. While 'horror' is the noun referring to the feeling of intense fear or dread itself, 'horroroso' is the adjective form describing something that causes or is full of horror.

English speakers can easily connect 'horroroso' to several familiar English words. The most obvious is 'horror', which shares the same Latin root and nearly identical meaning. The English adjective 'horrendous' and 'horrible' also come from the same Latin root 'horrere'. Even the word 'horrific' shows this connection. Notice how English uses different suffixes (-ible, -endous, -ific) to form adjectives where Spanish uses -oso, but they all convey similar meanings of something causing horror or fear.