Young children make up a lot of silly and nonsense words, and also make up a lot of euphemisms for "dirty" words to avoid getting in trouble. Taken together, these factors result in there being quite a few baby-talk and kid-talk words for the (ahem) virile member. Here are a few of these; I'm sure other noders can think of more. Because different families may teach their sons different words for their anatomy -- indeed, may teach two sons different words from one another -- the choice of such a word may be considered idiolect. Since these words are almost exclusively spoken, they rarely have standard spelling.

One commonality among these expressions is that they refer to the use of the penis for urination. This makes sense, since that is all a very young boy is likely to use his penis for. Contrast these with more "adult" slang expressions for the member, such as "cock", which refer to virility.