Aww, your LO is so cute!
|Smol||Small and cute|
|Chungus||A cute, chunky creature|
|Pet parents||Pet owners that treat their pet like a child|
|Tiger mother||A mom who demands excellence from her child|
Parents and others who interact with small children use LO to mean "little one." This acronym is a short and sweet way to refer to a short and sweet kid.
Typically, parents use LO when discussing their own child. For example, a friend who has a small child may send you "can't make it out tonight, LO really acting up" to let you know they'll be busy parenting this evening. (Parenting: The fullest of full-time jobs, amirite?)
As a child ages up toward tweendom, their parents may stop referring to them as an LO. However, the child will likely always be an LO in their parents' hearts.