The “lootenant” of the Australian Navy is equivalent to a higher rank in the Australian Army then their own “leftenant”. That is, the different pronunciations are used, as far as I can ascertain, to denote the differences in seniority between the ranks. Calling an Australian Navy Lieutenant, “leftenant” then, would be something like calling an Australian Army Colonel a Major. This would be both very rude, if done deliberately, and very embarrassing. You would no doubt be in a lot of trouble, especially if you were addressing them in a formal situation, as it would be a big no no in etiquette and most definitely a social faux-pas. Interestingly, my father’s (once a Lieutenant Colonel himself) copy of the “Customs of the Army” handbook says:
“65. Mode of Address. It is normal good manners to address a person by his correct title and an officer must be able to recognise the badges of rank of the other Services. It should be noted that these ranks are always used in full except that:
c. Naval Lieutenants are not called “Mister” and Lieutenant is always pronounced “L’tenant” ”
His copy of the handbook was published in 1965 “by command of the Military Board”.
All very interesting.
[Edit] An Australian Navy "Lootenant" is equivalent to an Australian Army Captain. Just in case you wanted to know. [/Edit]