'ammonical' originates from 'ammonia', specifically the word 'ammoniacus', where 'ammon' referred to the ancient Egyptian god Amun, associated with the region where ammonium chloride was first discovered.

'ammoniacus' transformed into the English word 'ammoniacal', and eventually became the modern English word 'ammonical'.

Initially, it meant 'pertaining to ammonia', and this meaning has largely remained the same in modern usage.