1 COR 4 :6 Now, brethren, if I come unto you speaking with tongues, what shall I profit you, except I shall speak to you either by revelation, or by knowledge, or by prophesying, or by doctrine?

Speaking in tongues used the Greek verb laleo. This is a word used many times in the Scripture.

As far as speaking in tongues it is used in reference to the manifestation of tongues

! Cor 12 :3  « speaking by the spirit of God. This may be speaking in tongues or prophecy or interpretation of tongues. All are speaking by the spirit of God. All these three are speaking manifestation.

1Co 12:30

Have all the gifts of healing? do all speak with tongues? do all interpret?

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In these verses laleo is used and may be refering to the speaking manifestations.

1Co 2:6

Howbeit we speak wisdom among them that are perfect: yet not the wisdom of this world, nor of the princes of this world, that come to nought:

1Co 2:7

But we speak the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory:

Co 2:13

Which things also we speak, not in the words which man’s wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual.

Laleo in Ancient Greek meant to talk, speak, chatter or chirp.  It proabably came from the onomatopea « lalalala » since latin has LLalo for lulaby and German llalen for babble.  The adjective in Greek LLalos is babbling.

There are different words translated from Greek to speak and they each have a certain meaning

Lego means properly, to “lay” forth, i.e. (figuratively) to say but relate (in wordso say, affirm, teach, usually of systematic or set discourse.

Eipon and Phemi generally refer to an individual expression or speech respectively;

Eipon to speak or say (by word or writing):—answer, bid, bring word, call, command, grant, say (on), speak, tell.

Phemi means to say but to make known one’s thoughts, to declare

Reo means to say but, properly flow but by breaking the silence,

Laleo means say but means to flow with an extended or random rant or diatribe.

Laleo is defined by Strongs Greek as follows

1. to utter a voice, emit a sound: of things inanimate,
2. to speak, i. e. to use the tongue or the faculty of speech; to utter articulate sounds
3. to talk
4. to utter, tell: with the accusative of the thing,
5. to use words in order to declare one’s mind and disclose one’s thoughts; to speak

LALEO
Mat 10:19-20

But when they deliver you up, take no thought how or what ye shall speak: for it shall be given you in that same hour what ye shall speak. For it is not ye that speak, but the Spirit of your Father which speaketh in you.

When we are given the utterance or sounds placed on vocal chords, it is Our Father, the True God speaking thorough us! 

Take no though “how” or “what”. When God’s spirit is speaking in us we are not to worry because He will control in what manner we speak and He will control the content of the woRds.