The noun toggle is the singular form; the plural form is toggles.

A toggle is a metal or wooden pin or rod, or similar, which helps you to secure things.

Because 'T' stands for 'Toggle'

The way to sew on a toggle button is to first pin the toggle button in place on the jacket. Next, take a threaded needle and knot it tightly. Insert the threaded needle through the loop in the toggle at least four or five times, securing the know underneath the fabric. Tie and knot and the toggle should be in place.

when dealing with bit, there are only 2 bits which are '0' and '1'. when the current bit is '0', if we toggle this bit, it will become '1' and when the current bit is '1', if we toggle this bit, it will become '0' that is