Didicoy is a term of the Romanichal (the English branch of Romani or "Gypsies") for travellers

Nomadic peoples of Europe

In Europe the settled lifestyle has long been the norm, but some small nomadic communities exist or have existed recently.- Romani :By far the most important and best known of these communities are the Romani people, traditionally known in English as Gypsies...

 with mixed Romani blood. There was often fierce competition between the groups, and the Romanichal tended to blame their own reputation for criminality on the didicoys and other nomadic groups masquerading as "Gypsies".

Some families of mixed blood would often call themselves "kyes" for short.

Often, the settled population of Britain's Romany use the term Didicoy as a slang expression for all Romani people.

An example of an old Romani song about a mixed blooded Romanichal is the "Romano Rai":

I'm a Romano Rai, just an old didikai,

I build all my temples beneath the blue sky,

I live in a tent and I don't pay no rent,

and that's why they call me the Romano Rai.

Didi-a-didi-a-didi-di-kai, chavves,

Tika-dika-tika-a-lai, (or can be; Kakka Chavve, Dekh akai)

Your Daddus tryin' to sell a mush a kushto grai.

I'm a Romano rai, just an old didikai,

I live in a mansion beneath the blue sky,

I was born in a ditch, so I won't ever grow rich,

But that's why they call me the Romano Rai.

Tikka, tikka, didikai, tikka, tikka, didikai

That's why they call him the Romano Rai

Tikka-tikka-didikai, tikka tikka, didikai,

That's why they call him the Romani Rai.

I'm a Romano Rai, a true didikai,

My temple's a mansion beneath the blue sky,

I'm a Romano Rai, a true didikai,

just campin' around, on any ol' ground,

But that's why they call him the Romano Rai.