Turcopolis/Turkopolis

If you mean Turcopoles, they were light cavalry/skirmishing force which is AFAIK mentioned both in service of Christian and Muslim armies during Crusading era in the Near East. Their origin was probably mixed.

While undoubtly, at least initially, the largest ethnic component was Turkic, often they became inhabitants of some non-Turkic land and eventually got assimilated.

Turcopoles first mention and  recruitment took place in the Byzantine army of 12th century (Komnenean era) as Turkopouloi.

They were actually light skirmishing fighters of mixed parentage (Greek-Turkish) and mostly christians.

In fact their name means sons of Turks in Greek (ending -opoulos/-oi like in many modern greek surnames-also medieval ones (etc .Fragopoulos,officer of Constantine Paleologos)

Such units of mixed origin in the byzantine army were also the Gasmouloi.
These had mixed Greek/Latin(=western European(mainly French/Italian)) parentage.
They served as marines or servants in the navy.

In my research I have found the Turkopoles were not the same as the Byzantine Turkopouloui.  Nor did the Turkopoles have any relations to the Turkoman. 

I use to think Turkopoles came from a specific ethnic group and were muslims.  This is not the case.  Turkopoles came from many different areas, the Levant, Byzantium, Anatolia, and Europe.  This is supported by an incident that happened during the 3rd crusade.  2 Turkopoles and a Bedouin were sent to reconnoiter a caravan.  The 3 were approached by those guarding/escorting the caravan.  Sources state only the Bedouin was to do the talking and the other two were to remain silent.  Had the Turkopoles spoke they would have been compromised.  What wasn't clear was whether or not the turkopoles spoke Arabic or not.  It does state they were dressed in Arab fashion.  It is clear however, that some Turkopoles did speak Arabic or Turkish.  During a siege (I forget which one, a Templar castle) the Mamlukes encouraged the Turkopoles to give up their loyalty to the Franks.  Many did so and climbed over the walls.  To prevent any further "desertions" the Templars enforced strict disciplinary actions against the Turkopoles. 

The role of the Turkopoles within the Latin armies was relegated to scouting, raiding, ambushes, skirmishing in small engagements, and during large battles they were used (as lightly armed shock cavalry) to augment the knights during the charge.  They did not deploy in front of the army and fight in the Turkoman fashion.  In many different sources the charge of the Frankish cavalry is described as "echelon".  Due to the lack of numbers there is no way the knights could have charged in echelon.  However, if they are backed up by sergeants and Turkopoles then the echelon is possible.

Brigham Young University.  Located in Provo, Utah, U.S.