godan verb (-ru), intransitive verb
grow on you; gradually become liked
Internet slang abbreviation of じわじわ来る. Describes something that was initially unappealing or unfunny but slowly becomes enjoyable or amusing over time.
At first it was meh, but this song has grown on me.
あの変なキャラ、見てるうちにじわるわ。
That weird character is starting to grow on me the more I see it.