Exodus 6:28-30 KJVS
 And it came to pass on the day when the Lord spake unto Moses in the land of Egypt,  That the Lord spake unto Moses, saying, I am the Lord : speak thou unto Pharaoh king of Egypt all that I say unto thee.  And Moses said before the Lord, Behold, I am of uncircumcised lips, and how shall Pharaoh hearken unto me?
So, you may be wondering. Why did Moses say “I am of uncircumcised lips” when addressing him speaking to pharaoh? Well, how did our forefathers view one that was and wasn’t circumcised?
Genesis 17:10-11 KJVS
 This is my covenant, which ye shall keep, between me and you and thy seed after thee; Every man child among you shall be circumcised.  And ye shall circumcise the flesh of your foreskin; and it shall be a token of the covenant betwixt me and you.
The covenant of circumcision was one in which the Most High established with our forefathers and was part of an intimately righteous relationship with him.
1 Samuel 17:36 KJVS
 Thy servant slew both the lion and the bear: and this uncircumcised Philistine shall be as one of them, seeing he hath defied the armies of the living God.
Being uncircumcised was an insult in the eyes of Israel. And was looked down upon.
Isaiah 52:1 KJVS
 Awake, awake; put on thy strength, O Zion; put on thy beautiful garments, O Jerusalem, the holy city: for henceforth there shall no more come into thee the uncircumcised and the unclean.
The Most High even associates being uncircumcised with being unclean. And being unclean can be seen as a euphemism for being dirty. However, the word is even used outside its literal context.
Leviticus 19:23-25 KJVS
 And when ye shall come into the land, and shall have planted all manner of trees for food, then ye shall count the fruit thereof as uncircumcised: three years shall it be as uncircumcised unto you: it shall not be eaten of.  But in the fourth year all the fruit thereof shall be holy to praise the Lord withal.  And in the fifth year shall ye eat of the fruit thereof, that it may yield unto you the increase thereof: I am the Lord your God.
Here we see uncircumcised was something not limited to foreskin but used in other applications as well. Trees and fruits cannot literally be circumcised or uncircumcised. We see the Most High used circumcision symbolically. That even if a tree begins to produce fruit, that fruit should not yet be eaten immediately after you plant a tree and it beings to produce, you should therefore view it as unclean. Don't deal with it.
So now when we revisit Moses and him being reluctant to speak unto Pharaoh we know Moses’ lips were not physically uncircumcised. However, Moses’ was looking at two main clauses. The first and most important was that who was he to the current Pharaoh? He was not a known king or prince, he did not have riches. He wasn’t even a noble nor invited to attend.
Exodus 6:10-11 KJVS
 And the Lord spake unto Moses, saying,  Go in, speak unto Pharaoh king of Egypt, that he let the children of Israel go out of his land.
The two scriptures above add context. In Moses’ mind, if I do this I will be laughed at because he will say, who are you?!? When approaching a king it would be likened similarly to a homeless man or woman on the streets saying give me thy car I have need of transportation. And the Lord says it is mine this day. You would laugh them to scorn. You would think what would make you fix your lips to ask such a thing. Let alone demand it. But this was similar to the very thing Moses is being told to say.
Exodus 4:10-12 KJVS
 And Moses said unto the Lord, O my Lord, I am not eloquent, neither heretofore, nor since thou hast spoken unto thy servant: but I am slow of speech, and of a slow tongue.  And the Lord said unto him, Who hath made man's mouth? or who maketh the dumb, or deaf, or the seeing, or the blind? have not I the Lord ?  Now therefore go, and I will be with thy mouth, and teach thee what thou shalt say.
Secondly, Moses understood he wasn’t the best orator. His speech wasn’t as clean or polished in terms of what one may expect from a “politician” or leader. He wasn’t as educated in moving or passionate speeches. And if one of the biggest things I have to do is persuade Pharaoh and give speeches shouldn’t you find someone more skilled? However, the most High knew what he saw in Moses and what attributes he needed overall to accomplish the mission. That when dealing with his people you would need a lot of patience.
Ephesians 4:2 KJVS
 With all lowliness and meekness, with longsuffering, forbearing one another in love;