According to the recent post from the Dbz fansite Kanzenshuu, the SS2 transformation was initially named "Super Saiyan grade 5", long before it was properly named when Goku stated the SS2 name in the Majin Buu arc. Why 5th grade some of you may ask? Thats because it includes the first 4 Super Saiyan forms/powerups of:
Super Saiyan 1
Super Saiyan grade 2/Ascended (The muscly power up achieved by Goku, Trunks and Vegeta)
Super Saiyan grade 3/Ultra (The even more muscly powerup that further increases strength but reduces speed achieved by Goku, Trunks and possibly Vegeta, Cell)
Super Saiyan Grade 4/Full power (The calm Super Saiyan state achieved by Goku and Gohan)
Super Saiyan Grade 5-Later known as Super Saiyan 2 (Achieved by Goku, Gohan, Vegeta and possibly others)
Interesting isnt it? For the people who love what-if's, I guess the term "SS5" technically existed in this manner, but not in the way you expected it.
Also, it seems Broly's Legendary Super Saiyan form was named differently initially as well: Known as Super Saiyan (Final Form) according to the forum post below.
Also to note: Super Saiyan Grade/Stage 2 is NOT Super Saiyan 2 as many fans confuse due to translation/fan-names etc.
Forum post based on said subject: www.kanzenshuu.com/forum/viewt…