illuc

Illuc belongs to a four-way system that English has largely lost, and getting it right is a matter of asking which question the adverb answers. Illuc answers quo, "to where?", and means motion towards that place. Illic answers ubi, "where?", position there. Illinc answers unde, "from where?", motion away. Ibi is the neutral "there". The matching near-deixis set is huc, hic, hinc.

So illuc always goes with a verb of motion, and putting it with a verb of rest is a real error, not a stylistic wobble. The pair huc illuc, "hither and thither", is fixed and describes aimless or agitated movement. English still has thither in the dictionary, which is exactly this word's job, but nobody has said it in earnest for two hundred years.