Not changing. Also meaningless noise on a channel — the same word for stillness and for interference.
Greek στατικός (statikos, causing to stand, stationary), from ἱστάναι (histanai, to stand); the later sense of meaningless noise on a channel grew from the electrical charge that makes things stand and cling rather than flow.
Not changing, and also the noise a channel carries when nothing meaningful is passing through it. Stillness and interference share one old word for standing.