The Spanish verb 'luchar' meaning 'to fight' or 'to struggle' comes directly from the Latin verb 'luctari', which meant 'to wrestle' or 'to struggle'. The evolution from Latin to Spanish shows a typical sound change where the Latin 'ct' cluster simplified to 'ch' in Spanish, while maintaining the core meaning of physical or metaphorical struggle.

Some related Spanish words include 'lucha' (the noun meaning 'fight' or 'struggle'), 'luchador' (fighter, wrestler), and 'luchadora' (female fighter). These words are all part of the same word family and share the basic concept of struggle or combat.

While there aren't many common English words directly related to 'luchar', we do have some technical or specialized terms from the same Latin root, such as 'reluctant' (originally meaning 'struggling against') and 'reluctance'. The prefix 're-' combined with the root 'luct-' gives us the sense of 'fighting back' or 'resisting', which evolved into our modern meaning of being unwilling or hesitant.