Google says:Amazon Kindle Fire.
Tap the button at the bottom of the screen, then select “Settings“. Scroll down and select “Clear all cookie data“, “Clear cache” or “Clear history” as desired. A dialog should appear where you can confirm your selection. Tap “OK” to proceed." So what youre doing is the equivalent.
He says you can try going into apps like facebook or what ever you have and try clearing any of their cached data but that might not be possible.
A more drastic option would be to save everything to another device and do a factory reset.