The Spanish word 'conejito' meaning 'little rabbit' comes from combining the Spanish word 'conejo' (rabbit) with the diminutive suffix '-ito'. The base word 'conejo' itself derives from the Latin word 'cuniculus', which also meant 'rabbit'. The diminutive suffix '-ito' is a very common and productive suffix in Spanish that adds the meaning of 'small' or expresses endearment.

The most obvious related Spanish word is 'conejo' (rabbit), which is the base word from which 'conejito' is formed. Understanding this relationship is straightforward - 'conejito' is simply a 'little conejo'. This pattern of adding '-ito' to create diminutives is very common in Spanish, as seen in pairs like gato/gatito (cat/kitten) and perro/perrito (dog/puppy).

While English doesn't have any common words directly related to 'conejito' or 'conejo', there is an interesting scientific connection. The Latin 'cuniculus' gave rise to the taxonomic name for rabbits, Oryctolagus cuniculus, and the scientific term 'cunicular' meaning 'relating to rabbits'. However, these terms are primarily used in scientific contexts and aren't part of everyday English vocabulary.