A placeholder term is a word with no meaning you use it to stand for a thing when you can't remember the name, or just any instance of something of a certain type. Examples would be English thingamobob/watchamacallit, Salvadoran Spanish volado 'watchamacallit' (or the cutesier coso, or the pejorative babosada). They can also be used for imaginary places or people, e.g. German Hintertupfingen 'bumfuck nowhere', English so-and-so.
Since the Hebrew geresh mark (or "chupchik") is even smaller than a yod (to recall that famous quote of Jesus'), presumably this just means 'watchamacallit'.
"jump scare", at least, goes back to the 1990s, if not older. "sus" (with 1 s) is definitely a new thing, but i've seen the suss spelling at least a few times before, where it can stand for suspicious or stand alone ("suss out"). Funnily enough it seems that poggers is actually from the 1990s as well, just not in its original sense. i remember playing pogs when i was young but i assumed unti now that it was just a coincidence.
