Abstruse - Big in the early 1800s according to the Google Ngram Viewer. https://books.google.com/ngrams/graph?year_start=1800&year_end=2008&corpus=15&smoothing=

Abstruse - Big in the early 1800s according to the Google Ngram Viewer. https://books.google.com/ngrams/graph?year_start=1800&year_end=2008&corpus=15&smoothing=7&case_insensitive=on&content=abstruse&direct_url=t1%3B%2Cabstruse%3B%2Cc0 https://books.google.com/ngrams/graph?year_start=1800&year_e...