'anxiousness' originates from Latin, specifically the word 'anxius', where the root 'angere' meant 'to choke or strangle' (figuratively, to cause distress); the suffix '-ness' comes from Old English '-nēs(s)e', used to form nouns.

'anxiousness' developed from the adjective 'anxious' (from Latin 'anxius' via Old French 'anxieux' and Middle English), with the addition of the noun-forming suffix '-ness' to create the modern English noun 'anxiousness'.

Initially it conveyed being 'troubled or mentally distressed'; over time it evolved to the current primary meaning of 'a state of worry or unease' and also acquired the secondary sense of 'eagerness' in some contexts.