The Spanish word 'orco' (meaning 'orc' or 'ogre') comes from the Latin word 'Orcus', which referred to a god of the underworld and death in Roman mythology. This evolution from a specific underworld deity to a more general monstrous creature reflects how ancient mythological figures often transformed into broader folkloric concepts over time. The semantic shift from 'god of death' to 'monster/ogre' is quite natural, as both concepts are associated with darkness, fear, and the supernatural.

While 'orco' is a relatively unique word in Spanish, it has become more widely known in recent decades due to fantasy literature and games. There aren't many common Spanish words directly related to it etymologically, as it comes from a very specific mythological term.

The English word 'orc' is a cognate of Spanish 'orco', though it entered English through a different route. J.R.R. Tolkien popularized 'orc' in modern fantasy literature through 'The Lord of the Rings', drawing from Old English 'orcneas' (evil spirits), which ultimately relates to the same Latin 'Orcus'. This shared etymology explains why both Spanish 'orco' and English 'orc' refer to similar monstrous creatures in modern fantasy contexts.