'bandiness' originates from English, formed from the adjective 'bandy' plus the suffix '-ness' (Old English-derived suffix denoting a state or condition).

'bandy' came into Middle English (as 'bandy(e)') influenced by older Germanic roots related to bending (compare Old Norse 'benda' / Old English 'bend' family), and later took on both senses of 'bent/curved' and 'to toss back and forth'; the modern noun 'bandiness' developed by adding '-ness' to 'bandy'.

Initially associated with the idea of being 'bent' or 'curved' (especially of limbs), over time 'bandy' acquired an additional sense 'to pass back and forth' (of words or objects); consequently 'bandiness' can refer either to curvedness or to the quality of exchanging/bantering.