'prototypicality' is formed in English from the adjective 'prototypical' + the nominalizing suffix '-ity'. 'Prototype' itself originates from Greek 'prototypon' (protos + typos), where 'proto-' meant 'first' and 'typos' meant 'impression, model'.

'Prototype' entered English via Latin/French from Greek 'prototypon'; the adjective 'prototypical' was created in modern English from 'prototype' + '-ical', and later the noun 'prototypicality' was formed by adding the suffix '-ity' to that adjective to denote the state or degree of being prototypical.

Initially connected to the idea of being a 'first model' or 'original pattern' (a prototype); over time the focus shifted to denote the degree to which something is representative or typical of a category (its typicality), yielding the current meaning of 'prototypicality' as a measure of representativeness.