From BiblePortal Wikipedia

Hawker's Poor Man's Concordance And Dictionary [1]

So called from Peleth, meaning judges. The Pelethites and Cherithites (or Cherim, more properly speaking) were much spoken of in the days of David. ( 1 Samuel 30:14 and  2 Samuel 8:18) It should seem to have been an office in the inferior courts for judging the people; hence the Pelethites and Cherithites were judges. The word Cherim means excommunication: and there were three degrees of it observed. The first was a simple separating, called Niddui; the second Cherim, somewhat like what the apostle calls Anathema Maranatha; and the third implied death, and was called Shammathah.

Fausset's Bible Dictionary [2]

(See Cherethites .) The two together formed David's body guard. As Ittai of Gath, so other refugees from Philistine tribes probably joined David. The Egyptian monuments mention Shayretana ("Cherethim" or "Cretans") and Ρelesatu ("Philistines"), whom Rameses III conquered. The Shayretana supplied mercenaries to the Egyptian kings of the 19th and 20th dynasties. Cherethites may be from Chaarat "to cut off," namely, from one's country; Pelethites from Paalat "he fled," "fugitives," political refugees. "Philistine" is from phalash "to emigrate." Gesenius less probably explains" executioners and runners."

Morrish Bible Dictionary [3]

These formed a part of David's guard. They are always grouped with the Cherethites. It is uncertain from whence they came or what the name signifies.  2 Samuel 8:18;  2 Samuel 15:18;  2 Samuel 20:7,23;  1 Kings 1:38,44;  1 Chronicles 18:17 . Gesenius calls them 'public couriers,' doubtless because peleth means 'swiftness.' The LXX and Vulgate leave the name untranslated. Some trace the word to the Philistines.

American Tract Society Bible Dictionary [4]

Are always mentioned together with the Cherethites, as constituting the king's bodyguard,  2 Samuel 8:18   22:23 . The word, if not the name of a Jewish or a Philistine family, is supposed to signify runners; and thus they would seem to have been the royal messengers; just as the Cherethites, from a Hebrew word signifying to cut off, were the king's executioners. See CHERETHITES.

Easton's Bible Dictionary [5]

 2 Samuel 8:18 2 Samuel 1:38,44 1 Chronicles 18:17 2 Samuel 15:18

Hastings' Dictionary of the Bible [6]

PELETHITES. See Cherethites and Pelethites.

Holman Bible Dictionary [7]

 2 Samuel 8:18

International Standard Bible Encyclopedia [8]

pel´ḗ - thı̄ts , pē´leth - ı̄ts ( פּלתי , pelēthı̄ ): A company of David's bodyguard, like the Cherethites (which see) ( 2 Samuel 8:18;  2 Samuel 15:18 ); probably a corrupt form of "Philistines."