Seaman 2nd Class was renamed to Seaman Apprentice in 1948. The rate was originally established as ordinary seaman in 1797 and renamed to Seaman 2nd Class in 1917.
And to add onto the Navy’s fucking with rates and ratings throughout the centuries:
Seaman Recruit was originally Landsman. Landsman (the LDS you see on old gravestones) existed from 1838 to 1921 when it went through a series of morphing to what is now seaman recruit.
Seaman existed from 1797 until it was renamed Seaman 1st Class in 1917. Then it went back to Seaman in 1948.
Coal Heaver was established in 1842. Renamed to Coal Passer in 1893. Renamed to Fireman 3rd Class in 1917 and finally to Fireman Recruit in 1948.
Fireman was established in 1842. It was split into paygrades Fireman 1st Class and Fireman 2nd Class in 1847. Fireman 1st class became Fireman in 1948, Fireman 2nd class became Fireman Apprentice in 1948. I’ll have to look up the exact year, but prior to the 1880s, a Coal Heaver could in theory work his way up through FN 1c and FN 2c and then obtain a commission as a 3rd Assistant Engineer and then work his way up to Chief Engineer. There’s a whole section of the historical fuckery and abuse engineering officers went through in the book “Waiting for Dead Men’s Shoes” by Donald Chisholm if you want a Navy history book to add to your reading list.
And onto the rating fuckery:
Prior to 1885 all sailors were undes. Prior to that year, the rating you held was only temporary and changed from command to command depending on the whims of your CO. Spend a decade in the Navy starting either as a Landman or a Boy if you enlisted at 16 and work your way up to Seaman. Merchant Marine sailors could come in as an ordinary seaman. Collect a few LOAs, keep your nose out of trouble and maybe at your next command the skipper will decide that you were going to be a MA or a BM or perhaps a GM or one of a couple other petty officer ratings that no longer exist. Go to your next command and chances are very good that you won’t have the same rating since someone else already has it. If you have a liberty incident involving alcohol, chances are highly likely that you will be dis-rated as punishment.