The Spanish word 'mulita' comes from the Latin word 'mula' meaning 'female mule'. In Spanish, 'mula' retained this meaning, and the diminutive suffix '-ita' was added to create 'mulita', literally meaning 'little female mule'.

The diminutive suffix '-ita' is very common in Spanish and is used to indicate smallness or endearment. When added to 'mula', it creates a more affectionate or diminutive form of the word.

The most obvious related Spanish word is 'mula' (female mule), from which 'mulita' is directly derived. Spanish speakers will also recognize the very common diminutive suffix '-ita' which appears in many Spanish words like 'casita' (little house), 'perrita' (little female dog), and 'mesita' (little table).

The English word 'mule' is related to 'mulita', as both come from the Latin 'mula'. While English uses 'mule' for both male and female animals, Spanish makes the gender distinction with 'mulo' (male) and 'mula' (female).