It's Mouse Keys option.
With Mouse Keys, you can move the mouse pointer and press the mouse button using the keyboard or numeric keypad. To turn on Mouse Keys, choose Apple menu > System Preferences, click Accessibility, click Mouse & Trackpad, then select the checkbox.
Open the Mouse & Trackpad pane of Accessibility preferences
The following illustration shows the keys to use on a keyboard (the keys on the left) and on a numeric keypad (the keys on the right) when Mouse Keys is on.
Keys that move the mouse pointer when Mouse Keys is on.
To move the mouse pointer:
With a numeric keypad: Use the 7, 8, 9, 4, 6, 1, 2, 3 keys on the keypad.
With the keyboard: Use the 7, 8, 9, U, O, J, K, L keys.
To click a mouse button:
With a numeric keypad: Press 5 on the keypad.
With the keyboard: Press I.
Thus 'I' is indeed mouse click!
Apple menu > System Preferences, click Accessibility, click Mouse & Trackpad and turn this off! Especially five times option.