'avariciousness' ultimately traces back to Latin: 'avaritia' (meaning 'greed'), from 'avarus' meaning 'greedy'. The English adjective 'avaricious' is formed from 'avarice' + '-ous', and '-ness' was added to form the noun 'avariciousness'.

'avaritia' (Latin) > 'avarice' (Old French/Latin-derived) > Middle English 'avarice' > adjective 'avaricious' (formed in Early Modern English) > noun 'avariciousness' (formed by adding '-ness' to 'avaricious').

Originally referring specifically to greed for wealth ('avaritia' = 'greed'), the sense has largely remained stable: today 'avariciousness' denotes intense or insatiable desire for wealth or material gain.