'non-yellowish' originates from two elements: the prefix 'non-' (from Latin 'non', meaning 'not') and the adjective 'yellowish' (from Old English 'geolu'/'geolwe' meaning 'yellow', with the suffix '-ish' forming adjectives).

'yellow' descended from Old English 'geolu' (and Middle English forms like 'yelwe'), which developed into modern English 'yellow'; the adjective 'yellowish' formed by adding the suffix '-ish' in Middle English. The negative prefix 'non-' was adopted in English (via Latin/Old French influence) to create words meaning 'not X', producing 'non-yellowish' as a modern compound.

Initially the roots referred specifically to the color 'yellow'; over time the suffix '-ish' formed 'yellowish' meaning 'somewhat yellow', and adding 'non-' produces the current meaning 'not yellowish'.