The word "utmost" refers to the greatest degree or the highest level of something. It is often used to describe the maximum extent of a quality, effort, or importance. When you say something is done to the utmost, it means it is done with the highest intensity or effort possible.
The word "utmost" comes from the Old English "ūtmōst" which is a combination of "ūte" meaning 'out' and "mōst" meaning 'most'. Thus, it literally refers to the "most out" or the farthest or extremest point.