We all know that abracadabra! is the cry of magicians and conjurers, as old fashioned as it may be. Hiccius doccius, however, belongs to jugglers.
Its usage is very similar: the juggler says hiccius doccius as they perform their feat or trick. The origin of hiccius doccius is not clear. It could be a modification of the Latin phrase hicce est doctus, which means ‘this or here is the learned man’ (Oxford English Dictionary), or it could simply be nonsense that imitates Latin. It has been in use since at least the late 17th century.
“In sadness, I think they are both jugglers: here is nothing, and here is nothing; and then hiccius doccius, and they are both here again.”
– John Dryden, Amphitryon, 1690