DD has SN (she had speech and language delay too, but is 13yo now). Her first word was at 16mo, and was num-nums for food.
DS1's first word wasn't a 'word' as such. At 9mo, he turned to me and said "want juice mummy please". I fell off my seat as he'd not said a word up to that point, and wasn't expecting it so early. (still a clever clogs now at 9yo).
DS2 has severe speech and language delay, he said his first word at 3years5months old, and it was mum. He is now almost 8yo, speaks ok, but his syntax is still very...off kilter. He talks a bit like Yoda, but at least he talks now!
DS3 - first word, mumumum, at 6mo, he DOES use it with purpose, too. He is now almost 7.5mo, and says mik mik for milk, bik for biscuit, ojjjj for orange (his orange blankie that he loves), bubbles (he also loves bubbles...), mum, adadad for DS2's name, og for DS1's name, and jjjjj for DD's name. Oh, and bum when he's doing a poo. Talkative little begger, him. Just like DS1.