>>140
https://en.wikipedia.org/wiki/Hull_classification_symbol#United_States_Navy_hull_classification_codes
It is important to understand that hull number letter prefixes are not acronyms, and should not be carelessly treated as abbreviations of ship type classifications.
Thus, "DD" does not stand for anything more than "Destroyer". "SS" simply means "Submarine". And "FF" is the post-1975 type code for "Frigate."

艦種記号（ハルナンバー）は頭文字でも略称でもないというのが米海軍の公式な見解。
AVGのGも水上機母艦などとの区別のために付けただけ。