Cooler and cold deck both originate from live poker where someone switches the deck in play to a stacked deck, probably using some kind of sleight of hand.
The new deck is designed to have a situation where you cant help but lose all your money.

Once a deck has been in play for a while the cards are slightly warmed up by the players and dealers hands. The new, stacked deck is therefore a "cold deck".

These days it doesnt imply any kind of cheating and just means a situation where you just get unlucky and cant help but lose your money because of cards/ stacks/ situation or whatever.

A heater is the opposite and I guess the term heater probably came around later as an opposite to cooler.