Originally Posted by Pestle:
If he starts it again after he's done teething, it's very common for kids to bit when they're on the cusp of becoming fully verbal. They get aggressive and frustrated when they want to communicate but can't. For one kid, I put together a "bitey box" of differently-textured toys that his parents sent in: One firm but flexible, one hard, one soft. When I saw him get ready to go in for a bite, I'd say "Go get your bitey box!" and he'd pick out a toy and spend the next few minutes walking around with the toy jutting from his teeth like Winston Churchill with a cigar in his mouth. 
I had a group of children who went through a biting stage so I put together a Biting Toys box and put a photo of a mouth with big teeth on it.
When it's just one or two biting I sometimes attach a small teether to the child's clothing with a pacifier clip so they've always got something on hand.