hi, hello · An expression of intensity (in some expressions); hey · A filler, in some expressions; hey
köken: Derived from Old Norse hei, likely from Low German hei or German hei, both from Latin hei (“oh! ah!”), of natural exclamatory origin. First attested in 1541.
hi (greeting) · hey (to get someone's attention) · bye (often repeated twice: hei hei)
köken: From Proto-Finnic *hei (compare Estonian hei, Ingrian hei, Karelian hei, Ludian hei, Veps hei). Compare also Old Norse hei (whence Swedish hej) and English hey.
expression used to call the attention of somebody: hey!
köken: Probably a natural expression, as may be inferred from its presence with similar meaning in many other unrelated languages: English hoy, Dutch hoi, Japanese おい (oi), etc.