It’s about time. We are now on Instagram!
c.1600, "cheating;" present participle adjective from amuse (v.). Sense of "interesting" is from 1712; that of "pleasantly entertaining, tickling to the fancy" is from 1826. Noted late 1920s as a vogue word. Amusive has been tried in all senses since 18c. and might be useful, but it never caught on. Related: Amusingly.