The Spanish word 'casita' comes from combining the Spanish word 'casa' (meaning 'house') with the diminutive suffix '-ita'. The base word 'casa' itself comes from Latin 'casa', which originally meant 'hut' or 'cottage'. Over time, in Spanish, 'casa' broadened its meaning to refer to any house, not just a small dwelling. When combined with the diminutive suffix '-ita', which is used to indicate smallness or endearment in Spanish, we get 'casita' meaning 'small house' or 'little house'.

The most obvious related Spanish word is 'casa', which is one of the first words Spanish students learn. While 'casa' means any house regardless of size, 'casita' specifically refers to a small house. Understanding this relationship helps reinforce how the diminutive suffix '-ita' modifies the meaning of the base word.

While English doesn't have any common words directly derived from Latin 'casa', English speakers might be familiar with the word 'casino', which ultimately comes from Italian 'casino', meaning 'little house' (similar to Spanish 'casita'). Originally, a casino was a small villa for pleasure, before it took on its modern meaning of a gambling house. The word 'cassette' also shares this etymology, as it originally meant 'little box' or 'little case'.