persistence; single-mindedness; sticking to one thing
Describes a person who stubbornly insists on one approach, opinion, or activity, often to the exclusion of alternatives. Can carry a slightly negative nuance of inflexibility.
He stubbornly sticks to his own opinion and won't listen to others.
That kid is completely obsessed with games and doesn't study at all.
always betting on the same thing
Original literal meaning from gambling: repeatedly placing the same bet. Now mostly used in figurative contexts or when explaining the etymology of the word.
Originally, 'ittenbari' referred to sticking to the same bet.