The first documents to we you notice that they bring back the name of our country go back to the low Middle Ages.  In 1261 in a stipulated legal action between canonical of the Saint George near Legnano and Torriani family the Canegrate name is already recorded. 
Other important testimony is the 'Liber Notitiae Sanctorum Mediolanensis', a directory of churches of the diocese of Milan written up from Goffredo from Bussero towards the end of 1200.  In this report the Bussero cited the Canegrate name next with that one of Canegrae.  The reasons of such double denomination are disowned, but probably it was caused from one already then little clear acquaintance of the origins of the etimo. 
We think that the local speech in succeeding itself of the generations and going itself to add to the lack of registrations or documents, has ingendered one sure confusion.  In fact, in an other document, 'the statutos of the roads and waters of the made peasantry of Milan in 1346', appear the name of Canegra, ulterior test, this, to our warning, than the oral tradition it can have drawn in deceit the authors or the copisti of the age.  In the centuries succeeded to you but the Canegrate name it was prevailed definitively. 
Recently they have been advanced several hypotheses on the origins and the meant one of the etimo in issue;  of it we bring back more notes: 

Canis in ager = dog in the field (from the Latin); 
Ca' Negrate = blackened houses;  
Cane (guarded behind) Grata = fantasy thesis, but sure not immotivata, in how much thought that the name of the country was derived from a specific activity of its inhabitants and that is the breeding of the dogs;  someone, remembering the use of some medioevali getlteman to make to raise and to guard the own dogs from hunting from the peasants, had thought that all that had ended in order to call the village.  Such historical reconstruction probably suggested puts into effect it them communal coat of arms.

The explanation that appears more scientifically deepened and perhaps definitive, is that one of professor the Flechia, that Latin origin characterizes in the name of our country one:  Canegrate to I winnow of the etimologica analysis would appear in its original shape like Cannetulatae, deriving from the Cannetum Latin = cane field, and indicating one characteristic acclimatizes them of some centuries orsono.  This last hypothesis is brought back in the 'Dictionary of Lombardic Toponomastica' of professor the D. Olivieri, than admitting it puts it in doubt the supposizione of professor the Rohlfs, that it sees in Canegrate the most ancient celtica matrix Cannicus.  To this purpose it goes but reported that archaeological ritrovamenti would indicate just one celtica inhabited presence of our territory. 

Other interesting issue is that one regarding the dialetto canegratese.  In fact, professor the Marinoni thinks that such speech belongs to an extended from Liguria linguistica island from Parabiago to Fagnano Olona and Busto Arsizio to Saronno. 

In this territory the speech of theLibero-Ligure population would have been maintained in the course of the centuries, alternating itself only partially with the successive invasions, above all that celtica of IV the century a.C..

The From Liguria tribes therefore would have stirred themselves with those Gaulish ones, losing in part their ethnic characteristics but conserving some linguistiche peculiarities. 
This last then, resisting for all the roman age, they ended in order to characterize the Latin language speech in these places, when it 'regionalizzò' with the fall of the empire of the West (V century d.C.).