The Spanish word 'incognoscible' meaning 'unknowable' comes from the Latin 'incognoscibilis', which was formed from three Latin elements: the prefix 'in-' meaning 'not', the verb 'noscere' meaning 'to know', and the suffix '-ibilis' meaning 'able to be'. When these elements combined, they literally created a word meaning 'not able to be known' or 'unknowable'.

The formation follows a logical pattern: something that cannot be known (noscere) is made negative by 'in-' and the possibility is expressed by '-ibilis', creating a word for concepts or things that are impossible to know or understand.

Some related and simpler Spanish words include 'conocer' (to know, to meet) and 'conocimiento' (knowledge), which both come from the same Latin root 'noscere'. The negative prefix 'in-' is also very common in Spanish and appears in many words like 'imposible' (impossible) and 'invisible' (invisible), following the same pattern of negation.

English speakers might recognize this word's connection to several familiar terms. The Latin 'noscere' (to know) is related to English words like 'cognition' (the mental process of acquiring knowledge), 'recognize' (to know again), and 'notice' (to become aware of). The structure is also similar to English 'unknowable' and 'incognito' (unknown, especially a person concealing their identity), which share the same Latin roots.