Literally 'teeth reach to' — 齿 (teeth, by extension 'speech/mention') + 及 (to reach). Words 'reach the teeth' when you actually utter them. Mostly negated — 不齿及, 不足齿及.
register
Highly literary. In modern speech you'd say 提到 (tídào) or 说起 (shuōqǐ) instead. 齿及 belongs to formal essays, classical-style writing, or refined speech.
