pertinacious: sticking to an opinion, purpose, or design.
If you think about it, this word sounds similar to the word "tenacious" which means tending to keep a firm hold on something.
Pertinacious is derived from "tenex", the Latin word for "tenacious". The Latin verb "tenēre", which means "to hold", is also one of the word's roots.
Example: The pertinacious actress chained herself to a tree to bring attention to her environmental fight.
Until next week...
Stay Curious ;)