'anticeremonious' is formed from the prefix 'anti-' (from Greek 'anti-' meaning 'against' or 'opposite') combined with English 'ceremonious', which ultimately comes via Old French 'ceremonie' from Latin 'caerimonia' meaning 'religious rite' or 'ceremony'.

'ceremonious' entered English from Old French 'ceremonie' (from Latin 'caerimonia'); the modern English adjective 'anticeremonious' was created by adding the prefix 'anti-' to 'ceremonious' to express the idea 'not ceremonious'.

Originally a literal combination meaning 'against ceremony', it evolved into the adjective meaning 'not ceremonious; informal; lacking ritual or formality'.