The Spanish verb 'fatigar' comes directly from the Latin verb 'fatigare', which meant 'to tire' or 'to weary'. The word has maintained essentially the same meaning and similar form as it evolved from Latin to Spanish, with just minor phonological changes typical of Spanish development from Latin words.

A common related Spanish word is 'fatiga' (meaning 'fatigue' or 'weariness'), which is the noun form derived from the same root. You might also encounter 'fatigoso' (tiring, exhausting) and 'fatigado' (tired, fatigued) in Spanish.

English speakers can easily remember 'fatigar' by connecting it to the English word 'fatigue', which shares the same Latin ancestor 'fatigare'. The English word entered the language through Old French 'fatiguer'. Both the Spanish and English words maintain the core meaning of tiredness or exhaustion from their Latin root.