Seesaw and teeter totter are two names for the same piece of playground equipment. I grew up using the word teeter totter mostly, but was aware of seesaw, as it was used in books.
I was wondering whether it is a regional difference or a generational difference.
From thefreedictionary, I found that there are even more terms used for this equipment: tilt or a tilting board, teedle board, dandle or dandle board. Teeter or teeterboard, and teeter-totter, which is probably the most common term after seesaw. So it is indeed a regional term,
which also explains why Google Ngrams has no recorded use of teeter totter in British English:
Link to Ngram for seesaw teeter totter in British English
Yet, if seesaw was in use since before 1800, how and why did teeter totter come into use seemingly all of a sudden just before 1920?
Link to Ngram for seesaw teeter totter in American English