The Spanish word 'aquelarre', meaning 'witches' sabbath', comes from the Basque compound word 'akelarre'. This Basque term combines 'aker' meaning 'male goat' and 'larre' meaning 'meadow', literally translating to 'goat's meadow'. The term evolved from referring to a physical location where goats gathered to its current meaning in Spanish, referring to a gathering of witches. This semantic shift likely occurred due to the association of goats with witchcraft and devil worship in medieval European folklore, where the devil was often depicted in the form of a goat presiding over witches' meetings.

Since 'aquelarre' comes from Basque rather than Latin roots, there aren't many etymologically related simpler Spanish words. This word stands somewhat isolated in Spanish vocabulary due to its unique Basque origin.

There aren't any directly related English words since 'aquelarre' comes from Basque, which is a language isolate (not related to Indo-European languages like English and Spanish). However, English speakers might find it interesting that while English uses the term 'witches' sabbath' for this concept, Spanish borrowed a term that literally meant 'goat's meadow' from Basque.