This is the 7281st most frequent Chinese word.
老三
"老三" means "the third child" or "the third eldest" in a family.
老三 is used here to refer to the third sibling or child in a sequence of birth order.
他是家里的老三。
He is the third child in the family.
老三 here might be a nickname used for a person associated with the dish, possibly the third sibling in a family who is renowned for this recipe.
这家餐馆的招牌菜是“老三炖肉”。
The specialty dish of this restaurant is 'Third Bro's Braised Meat'.
老三 in this context is used metaphorically to describe someone who assumes a modest or less competitive role, possibly likened to the stereotypical traits attributed to the third in line.