Icebreaker is a term that bloggers might be using in various ways. They might be talking about the ships that cut through sea, river or canal ice, making a passage for other ships, or allowing scientific exploration. The first and perhaps most famous of these was the Russian Krasin, built in 1916.
Or they might be referring to a conversation gambit or action design to initiate or ease a conversation or other interaction among people who don't know each other well, or at all.
But it seems most likely that they are talking about a brand of outdoor woollen clothing using merino fleece originating from New Zealand to which some consider themselves addicted.