'crossness' ultimately derives from the adjective 'cross', which comes via Middle English from Old Norse/Old English forms (e.g. 'kross'/'cros') and ultimately from Latin 'crux', where 'crux' meant 'a cross (the Christian cross)'.

'cross' in Middle English (crosse) developed senses such as 'marked with a cross' and 'contrary', and the modern adjective 'cross' (meaning irritable or angry) arose in later Middle English; the noun 'crossness' was formed by adding the suffix '-ness' to denote the quality or state.

Initially related to being 'marked by a cross' or 'contrary', the sense shifted in Middle English toward 'ill-tempered' or 'irritable', and 'crossness' now denotes the state of being irritable or angry.