uiautomatorviewer - What does NAF stand for?

"Not Accessibility Friendly"

These are UI elements which are apparently interactive, but which don't have accessibility affordances like content descriptions.

From the source for AccessibilityNodeInfoDumper.java (part of uiautomator):

 * We're looking for UI controls that are enabled, clickable but have no
 * text nor content-description. Such controls configuration indicate an
 * interactive control is present in the UI and is most likely not
 * accessibility friendly. We refer to such controls here as NAF controls
 * (Not Accessibility Friendly)
 * @param node
 * @return false if a node fails the check, true if all is OK
private static boolean nafCheck(AccessibilityNodeInfo node) {
    boolean isNaf = node.isClickable() && node.isEnabled()
            && safeCharSeqToString(node.getContentDescription()).isEmpty()
            && safeCharSeqToString(node.getText()).isEmpty();
    if (!isNaf)
        return true;
    // check children since sometimes the containing element is clickable
    // and NAF but a child's text or description is available. Will assume
    // such layout as fine.
    return childNafCheck(node);

NAF stands for " Not Accessibility Friendly" .