The story
The concept was invented by Karl Schroeder in his novel Ventus (2000) and has been adopted by some members of the artificial intelligence community to describe the self-organizing properties of fine-grained distributed networks. The novel states that the word was deliberately chosen as an allusion to "silent Thalia", the muse of Nature. Entities are considered to exhibit thalience if they succeed in developing their own categories for understanding the world.
Etymology from Wiktionary, CC BY-SA 4.0.