The Spanish word 'fantasmagoría' comes from the French word 'fantasmagorie', which was created by combining two Ancient Greek elements: 'phantasma' meaning 'apparition' or 'phantom', and 'agora' meaning 'assembly' or 'gathering place'. The term was originally coined in French to describe a form of horror theater using early projection techniques to create ghostly images, essentially creating a 'gathering of phantoms' or 'phantom assembly'.

The word made its way from French into Spanish, maintaining a very similar form and meaning. In modern Spanish, 'fantasmagoría' refers to an illusion or phantasmagoria - a shifting series of imaginary or fantastic imagery, much like its original theatrical meaning.

Some simpler related Spanish words include 'fantasma' (ghost, phantom) and 'fantástico' (fantastic), which share the same Greek root 'phantasma'. These words maintain the connection to the supernatural or illusory aspects of the original meaning.

English speakers might recognize the connection to words like 'phantasm', 'phantom', and 'phantasmagoria' (the direct English cognate). These all derive from the same Greek 'phantasma'. The English word 'agora' is also directly borrowed from Greek, referring to an ancient Greek marketplace or public square, preserving the original 'gathering place' meaning of the second element.