'intimidatingness' is formed in modern English by adding the noun-forming suffix '-ness' to the adjective 'intimidating', which itself comes from the verb 'intimidate'.

'intimidate' originates from Late Latin 'intimidare' (to make timid), from Latin roots related to 'timēre' (to fear). The verb entered English via Late Latin (and possibly French) in the 16th century and gave rise to the adjective 'intimidating' and the noun formed with '-ness'.

Initially the root meant 'to make timid' or 'to frighten'; over time the sense broadened to 'to overawe, deter, or cause apprehension,' and the modern derived noun denotes the quality or degree of causing such fear or awe.