In Jeremiah 1:6, Jeremiah says to God, as it is often translated, "I do not know how to speak, for I am only a boy."
The word for "boy" in Hebrew is נער or na'ar. It can mean "boy", but it often times means "servant".
There are two thoughts about what is going on here. Perhaps Jeremiah is very young and so he is worried about knowing the right thing to say. Or na'ar could refer to Jeremiah being the son of a priest (see Jeremiah 1:1), and thus likely a priest himself. This could mean that Jeremiah is worried that already serving God as a priest precludes him from serving as a prophet.
Jeremiah is either the patron prophet for young clergy or for second career clergy, as my Old Testament professor Becky Wright once put it. Either way, this passage in Jeremiah is a sign to those of us who serve God that He will be with us when we speak in His name, no matter how nervous we may be.