Source: "Beyond the Pleasure Principle", Sigmund Freud, W.W. Norton & Company, 1961. Translated and edited by James Strachey.

The child was not at all precocious in his intellectual development.

At the age of one and a half he could say only a few comprehensive words; he could also make use of a number of sounds which expressed a meaning intelligible to those around him.

He was, however, on good terms with his parents and their one servant-girl, and tributes were paid to his being a "good boy".

He did not disturb his parents at night, he conscientiously obeyed orders not to touch certain things or go into certain rooms, and above all he never cried when his mother left him for a few hours.

At the same time, he was greatly attached to his mother, who had not only fed him herself but had also looked after him without any outside help. This good little boy, however, had an occasional disturbing habit of taking any small objects he could get hold of and throwing them away from him into a corner, under the bed, and so on, so that hunting for his toys and picking them up was often quite a business.

As he did this he gave vent to a loud, long-drawn-out "o-o-o-o", accompanied by an expression of interest and satisfaction. His mother [and I] were agreed in thinking that this was not a mere interjection but represented the German word "fort" ["gone"]. I eventually realized that it was a game and that the only use he made of any of his toys was to play "gone" with them.

One day I made an observation which confirmed my view. The child had a wooden reel with a piece of string tied around it. It never occurred to him to pull it along the floor behind him, for instance, and play at its being a carriage. What he did was to hold the reel by the string and very skillfully throw it over the edge of his curtained cot, so that it disappeared into it, at the same time uttering his expressive "o-o-o-o". He then pulled the reel out of the cot again by the string and hailed its reappearance with a joyful "da" ["there"].

This, then, was the complete game - disappearance and return. As a rule one only witnessed its first act, which was repeated untiringly as a game in itself, thought there is no doubt that the greater pleasure was attached to the second act.

The Interpretation of the game then became obvious. It was related to the child's great cultural achievement - the instinctual renunciation (that is, the renunciation of instinctual satisfaction) which he had made in allowing his mother to go away without protesting. He compensated himself for this, as it were, by himself staging the disappearance and return of the objects within his reach.