Why did king henry 2 call his youngest son, John "lackland"?

In general the eldest son inherited all the property which in this particular case included the kingship and various duchies, the second son entered the military. The third son entered the clergy. However being the third son of a king eliminated the clergy so the third son might inherit a minor duchy. Since John was the youngest son there was nothing left for him to inherit so his only recourse was to marry an heiress. Thus John had no lands to rule in his own right. The irony of history is that his brothers left no legitimate heirs and John became king.

He owned no land.

I don't think so.

He had no inheritance