The Spanish word 'lupanar' meaning 'brothel' comes directly from the Latin word of the same spelling and meaning. The Latin 'lupanar' was formed by combining two elements: 'lupa' meaning 'she-wolf' or metaphorically 'prostitute', and the suffix '-ar' which indicated a place. The metaphorical use of 'lupa' (she-wolf) to mean 'prostitute' in Latin likely arose from the association of wolves with predatory or outcast behavior in ancient Roman culture. Thus, a 'lupanar' literally meant 'place of the she-wolves' or 'place of prostitutes'.

This word represents an interesting case of how metaphorical meanings can become fixed in language, as the connection between wolves and this particular profession became so established that it generated its own location term.

While 'lupanar' is a relatively uncommon word in modern Spanish, it's worth noting that the Spanish word 'loba' (meaning 'she-wolf') comes from the same Latin root 'lupa'. However, in modern Spanish, 'loba' has lost the metaphorical meaning that its Latin ancestor had and is used only to refer to the female wolf animal.

While English doesn't have any common words directly related to 'lupanar', we do have some scientific terms that use the Latin 'lup-' root referring to wolves, such as 'lupine' (meaning 'wolf-like' or relating to wolves). The word 'lupus', the name for an autoimmune disease, also comes from Latin 'lupus' meaning 'wolf', which is the masculine form related to 'lupa'.