'anilinium' originates from the word 'aniline' combined with the chemical suffix '-ium'; 'aniline' came into European languages from Spanish 'anil' (from Arabic 'al-nīl') meaning 'indigo', while the suffix '-ium' is used in chemical nomenclature to denote a positively charged ion or related species.

'aniline' entered English via French 'aniline' in the 19th century (ultimately from Spanish 'anil' < Arabic 'al-nīl'), and the form 'anilinium' was later formed in chemical nomenclature by adding the suffix '-ium' to denote the protonated (cationic) form of aniline.

Initially, words related to 'anil' referred to the indigo dye or the plant source; over time 'aniline' came to denote the specific organic compound (C6H5NH2), and 'anilinium' specifically denotes its protonated cation (C6H5NH3+).