The Spanish word 'exigible' (meaning 'demandable' or 'that which can be demanded') comes from combining the Spanish verb 'exigir' ('to demand') with the suffix '-ble' (meaning 'able to be'). The verb 'exigir' itself comes from Latin 'exigere' meaning 'to demand', which was formed by combining the prefix 'ex-' ('out') with the Latin verb 'agere' ('to drive' or 'to do'). The combination of these elements literally suggested the idea of 'driving something out' which evolved to mean 'to demand' or 'to require'.

Some related and more common Spanish words include 'exigir' (to demand), 'exigente' (demanding), and 'exigencia' (demand, requirement). All these words share the same Latin root 'exigere' and maintain the core meaning of demanding or requiring something.

English speakers might recognize the connection to words like 'exact' and 'exigent', which come from the same Latin root 'exigere'. 'Exact' originally meant 'precisely demanded or measured', while 'exigent' refers to something demanding or requiring immediate attention. The shared etymology is visible in how all these words relate to demands or requirements.