While on the loo at 湘南台駅 I noticed several signs on the wall. One said something about, “if you see 落書き on the walls please inform a member of the station staff”. So, combining the kanji for drop & write a new word was presented to me. I guessed it could have been referring to graffiti and indeed, it does! I can’t quite follow the link between drop & write meaning graffiti, but oh well. Apparently this word is also used for doodles.