Actually tentacles in Japanese erotica predate the industrial revolution... see
Wikipaedia!If you think about it, it's like most other cultures who have an erotic mythos around playing with their food...
Just some examples off the top of my head:
Shepherds and Sheep in general, apparently rumored to be practiced just about anywhere there are sheep...
Pasiphae (mother of the Minotaur)
Leda and the Swan