Short answers, pulled from the story.
The word thing derives from Proto-Germanic þingą meaning appointed time and possibly originates in Proto-Indo-European *ten- meaning stretch. It appears in Old Norse as þing, Middle English as thing, and modern languages including Norwegian, Danish, Swedish, Faroese, Gutnish, and Norn as ting.
Tacitus made the first detailed description of a thing in 98 CE suggesting these were annual delegate-based meetings serving legal and military functions. The oldest written reference to a thing dates from 43 CE to 410 CE on a stone pillar found at Housesteads Roman Fort along Hadrian's Wall reading Deo Mars Thincsus.
During the Viking Age things served as public assemblies of free men functioning as parliaments and courts at local regional and supra-regional levels. Their purpose included solving disputes making political decisions holding religious rites and acting as balancing structures to reduce tribal feuds and avoid social disorder.
National legislatures incorporating the word thing include Iceland's Alþingi Denmark's Folketing and Norway's Storting. Self-governing territories such as Åland Faroe Islands Greenland and Isle of Man also use names like Lagting Løgting Landsting and Tynwald referencing the historical assembly tradition.
Notable thing sites include Thynghowe in Sherwood Forest Nottinghamshire rediscovered between 2005 and 2006 Dublin's Thingmote raised mound Dingwall in Scottish Highlands Tingwall in Orkney and Shetland and Þingvellir hosting Iceland's Althing. Haugating in Tønsberg served as a key site for proclaiming kings in Norway while Swedish assemblies featured large mounds rune-stones and road crossings.