'armomancy' originates from Modern coinage formed from Greek elements: specifically 'aroma' (Greek 'arōma') and 'manteia' meaning 'divination', where 'arōma' meant 'sweet spice, smell' and 'manteia' meant 'divination'.

'arōma' passed into Latin as 'aroma' and then into Modern English as 'aroma'; the Greek 'manteia' developed into the English suffix '-mancy' (via Latin and Medieval scholarly use) used to denote methods of divination, and the two elements were combined in modern coinage to form 'armomancy'.

Initially it denoted (by formation) 'divination by smell'; that original sense is retained in modern usage for this rare/technical coinage.